diff --git a/.deadcode-out b/.deadcode-out
index 18beb6ad8..29d3d7c70 100644
--- a/.deadcode-out
+++ b/.deadcode-out
@@ -30,7 +30,6 @@ code.gitea.io/gitea/models/asymkey
 
 code.gitea.io/gitea/models/auth
 	GetSourceByName
-	GetWebAuthnCredentialByID
 	WebAuthnCredentials
 
 code.gitea.io/gitea/models/db
diff --git a/models/user/email_address.go b/models/user/email_address.go
index 18bf6d0b8..50c0cfbfb 100644
--- a/models/user/email_address.go
+++ b/models/user/email_address.go
@@ -307,60 +307,6 @@ func updateActivation(ctx context.Context, email *EmailAddress, activate bool) e
 	return UpdateUserCols(ctx, user, "rands")
 }
 
-func MakeEmailPrimaryWithUser(ctx context.Context, user *User, email *EmailAddress) error {
-	ctx, committer, err := db.TxContext(ctx)
-	if err != nil {
-		return err
-	}
-	defer committer.Close()
-	sess := db.GetEngine(ctx)
-
-	// 1. Update user table
-	user.Email = email.Email
-	if _, err = sess.ID(user.ID).Cols("email").Update(user); err != nil {
-		return err
-	}
-
-	// 2. Update old primary email
-	if _, err = sess.Where("uid=? AND is_primary=?", email.UID, true).Cols("is_primary").Update(&EmailAddress{
-		IsPrimary: false,
-	}); err != nil {
-		return err
-	}
-
-	// 3. update new primary email
-	email.IsPrimary = true
-	if _, err = sess.ID(email.ID).Cols("is_primary").Update(email); err != nil {
-		return err
-	}
-
-	return committer.Commit()
-}
-
-// MakeEmailPrimary sets primary email address of given user.
-func MakeEmailPrimary(ctx context.Context, email *EmailAddress) error {
-	has, err := db.GetEngine(ctx).Get(email)
-	if err != nil {
-		return err
-	} else if !has {
-		return ErrEmailAddressNotExist{Email: email.Email}
-	}
-
-	if !email.IsActivated {
-		return ErrEmailNotActivated
-	}
-
-	user := &User{}
-	has, err = db.GetEngine(ctx).ID(email.UID).Get(user)
-	if err != nil {
-		return err
-	} else if !has {
-		return ErrUserNotExist{UID: email.UID}
-	}
-
-	return MakeEmailPrimaryWithUser(ctx, user, email)
-}
-
 // VerifyActiveEmailCode verifies active email code when active account
 func VerifyActiveEmailCode(ctx context.Context, code, email string) *EmailAddress {
 	if user := GetVerifyUser(ctx, code); user != nil {
diff --git a/models/user/email_address_test.go b/models/user/email_address_test.go
index 65befa566..94680b6bd 100644
--- a/models/user/email_address_test.go
+++ b/models/user/email_address_test.go
@@ -43,40 +43,6 @@ func TestIsEmailUsed(t *testing.T) {
 	assert.False(t, isExist)
 }
 
-func TestMakeEmailPrimary(t *testing.T) {
-	assert.NoError(t, unittest.PrepareTestDatabase())
-
-	email := &user_model.EmailAddress{
-		Email: "user567890@example.com",
-	}
-	err := user_model.MakeEmailPrimary(db.DefaultContext, email)
-	assert.Error(t, err)
-	assert.EqualError(t, err, user_model.ErrEmailAddressNotExist{Email: email.Email}.Error())
-
-	email = &user_model.EmailAddress{
-		Email: "user11@example.com",
-	}
-	err = user_model.MakeEmailPrimary(db.DefaultContext, email)
-	assert.Error(t, err)
-	assert.EqualError(t, err, user_model.ErrEmailNotActivated.Error())
-
-	email = &user_model.EmailAddress{
-		Email: "user9999999@example.com",
-	}
-	err = user_model.MakeEmailPrimary(db.DefaultContext, email)
-	assert.Error(t, err)
-	assert.True(t, user_model.IsErrUserNotExist(err))
-
-	email = &user_model.EmailAddress{
-		Email: "user101@example.com",
-	}
-	err = user_model.MakeEmailPrimary(db.DefaultContext, email)
-	assert.NoError(t, err)
-
-	user, _ := user_model.GetUserByID(db.DefaultContext, int64(10))
-	assert.Equal(t, "user101@example.com", user.Email)
-}
-
 func TestActivate(t *testing.T) {
 	assert.NoError(t, unittest.PrepareTestDatabase())
 
diff --git a/models/user/user.go b/models/user/user.go
index 69cd85a20..f6d649eaf 100644
--- a/models/user/user.go
+++ b/models/user/user.go
@@ -451,17 +451,22 @@ var emailToReplacer = strings.NewReplacer(
 )
 
 // EmailTo returns a string suitable to be put into a e-mail `To:` header.
-func (u *User) EmailTo() string {
+func (u *User) EmailTo(overrideMail ...string) string {
 	sanitizedDisplayName := emailToReplacer.Replace(u.DisplayName())
 
-	// should be an edge case but nice to have
-	if sanitizedDisplayName == u.Email {
-		return u.Email
+	email := u.Email
+	if len(overrideMail) > 0 {
+		email = overrideMail[0]
 	}
 
-	address, err := mail.ParseAddress(fmt.Sprintf("%s <%s>", sanitizedDisplayName, u.Email))
+	// should be an edge case but nice to have
+	if sanitizedDisplayName == email {
+		return email
+	}
+
+	address, err := mail.ParseAddress(fmt.Sprintf("%s <%s>", sanitizedDisplayName, email))
 	if err != nil {
-		return u.Email
+		return email
 	}
 
 	return address.String()
diff --git a/models/user/user_test.go b/models/user/user_test.go
index bf3fc801c..abeff078c 100644
--- a/models/user/user_test.go
+++ b/models/user/user_test.go
@@ -625,6 +625,11 @@ func TestEmailTo(t *testing.T) {
 			assert.EqualValues(t, testCase.result, testUser.EmailTo())
 		})
 	}
+
+	t.Run("Override user's email", func(t *testing.T) {
+		testUser := &user_model.User{FullName: "Christine Jorgensen", Email: "christine@test.com"}
+		assert.EqualValues(t, `"Christine Jorgensen" <christine@example.org>`, testUser.EmailTo("christine@example.org"))
+	})
 }
 
 func TestDisabledUserFeatures(t *testing.T) {
diff --git a/options/locale/locale_en-US.ini b/options/locale/locale_en-US.ini
index 2c34025be..5a7c182b3 100644
--- a/options/locale/locale_en-US.ini
+++ b/options/locale/locale_en-US.ini
@@ -498,7 +498,24 @@ register_notify.text_2 = You can sign into your account using your username: %s
 register_notify.text_3 = If someone else made this account for you, you will need to <a href="%s">set your password</a> first.
 
 reset_password = Recover your account
-reset_password.text = If this was you, please click the following link to recover your account within <b>%s</b>:
+reset_password.text_1 = The password for your account was just changed.
+
+password_change.subject = Your password has been changed
+password_change.text_1 = The password for your account was just changed.
+
+primary_mail_change.subject = Your primary mail has been changed
+primary_mail_change.text_1 = The primary mail of your account was just changed to %[1]s. This means that this e-mail address will no longer receive e-mail notifications for your account.
+
+totp_disabled.subject = TOTP has been disabled
+totp_disabled.text_1 = Time-based one-time password (TOTP) on your account was just disabled.
+totp_disabled.no_2fa = There are no other 2FA methods configured anymore, meaning it is no longer necessary to log into your account with 2FA.
+
+removed_security_key.subject = A security key has been removed
+removed_security_key.text_1 = Security key "%[1]s" has just been removed from your account.
+removed_security_key.no_2fa = There are no other 2FA methods configured anymore, meaning it is no longer necessary to log into your account with 2FA.
+
+account_security_caution.text_1 = If this was you, then you can safely ignore this mail.
+account_security_caution.text_2 = If this wasn't you, your account is compromised. Please contact the admins of this site.
 
 register_success = Registration successful
 
diff --git a/release-notes/4635.md b/release-notes/4635.md
new file mode 100644
index 000000000..42ace0c2f
--- /dev/null
+++ b/release-notes/4635.md
@@ -0,0 +1 @@
+Email notifications are now sent when account security changes are made: password changed, primary email changed (email sent to old primary mail), TOTP disabled or a security key removed.
diff --git a/routers/web/user/setting/account.go b/routers/web/user/setting/account.go
index 795ee59d5..d2d2d5bc4 100644
--- a/routers/web/user/setting/account.go
+++ b/routers/web/user/setting/account.go
@@ -104,7 +104,15 @@ func EmailPost(ctx *context.Context) {
 
 	// Make emailaddress primary.
 	if ctx.FormString("_method") == "PRIMARY" {
-		if err := user_model.MakeEmailPrimary(ctx, &user_model.EmailAddress{ID: ctx.FormInt64("id")}); err != nil {
+		id := ctx.FormInt64("id")
+		email, err := user_model.GetEmailAddressByID(ctx, ctx.Doer.ID, id)
+		if err != nil {
+			log.Error("GetEmailAddressByID(%d,%d) error: %v", ctx.Doer.ID, id, err)
+			ctx.Redirect(setting.AppSubURL + "/user/settings/account")
+			return
+		}
+
+		if err := user.MakeEmailAddressPrimary(ctx, ctx.Doer, email, true); err != nil {
 			ctx.ServerError("MakeEmailPrimary", err)
 			return
 		}
diff --git a/routers/web/user/setting/security/2fa.go b/routers/web/user/setting/security/2fa.go
index cd0910236..1b1d385af 100644
--- a/routers/web/user/setting/security/2fa.go
+++ b/routers/web/user/setting/security/2fa.go
@@ -18,6 +18,7 @@ import (
 	"code.gitea.io/gitea/modules/web"
 	"code.gitea.io/gitea/services/context"
 	"code.gitea.io/gitea/services/forms"
+	"code.gitea.io/gitea/services/mailer"
 
 	"github.com/pquerna/otp"
 	"github.com/pquerna/otp/totp"
@@ -78,6 +79,11 @@ func DisableTwoFactor(ctx *context.Context) {
 		return
 	}
 
+	if err := mailer.SendDisabledTOTP(ctx, ctx.Doer); err != nil {
+		ctx.ServerError("SendDisabledTOTP", err)
+		return
+	}
+
 	ctx.Flash.Success(ctx.Tr("settings.twofa_disabled"))
 	ctx.Redirect(setting.AppSubURL + "/user/settings/security")
 }
diff --git a/routers/web/user/setting/security/webauthn.go b/routers/web/user/setting/security/webauthn.go
index e382c8b9a..bfbc06c70 100644
--- a/routers/web/user/setting/security/webauthn.go
+++ b/routers/web/user/setting/security/webauthn.go
@@ -16,6 +16,7 @@ import (
 	"code.gitea.io/gitea/modules/web"
 	"code.gitea.io/gitea/services/context"
 	"code.gitea.io/gitea/services/forms"
+	"code.gitea.io/gitea/services/mailer"
 
 	"github.com/go-webauthn/webauthn/protocol"
 	"github.com/go-webauthn/webauthn/webauthn"
@@ -112,9 +113,25 @@ func WebauthnRegisterPost(ctx *context.Context) {
 // WebauthnDelete deletes an security key by id
 func WebauthnDelete(ctx *context.Context) {
 	form := web.GetForm(ctx).(*forms.WebauthnDeleteForm)
+	cred, err := auth.GetWebAuthnCredentialByID(ctx, form.ID)
+	if err != nil || cred.UserID != ctx.Doer.ID {
+		if err != nil && !auth.IsErrWebAuthnCredentialNotExist(err) {
+			log.Error("GetWebAuthnCredentialByID: %v", err)
+		}
+
+		ctx.JSONRedirect(setting.AppSubURL + "/user/settings/security")
+		return
+	}
+
 	if _, err := auth.DeleteCredential(ctx, form.ID, ctx.Doer.ID); err != nil {
 		ctx.ServerError("GetWebAuthnCredentialByID", err)
 		return
 	}
+
+	if err := mailer.SendRemovedSecurityKey(ctx, ctx.Doer, cred.Name); err != nil {
+		ctx.ServerError("SendRemovedSecurityKey", err)
+		return
+	}
+
 	ctx.JSONRedirect(setting.AppSubURL + "/user/settings/security")
 }
diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index 38e292e6a..87df3d139 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -17,6 +17,7 @@ import (
 	"time"
 
 	activities_model "code.gitea.io/gitea/models/activities"
+	auth_model "code.gitea.io/gitea/models/auth"
 	issues_model "code.gitea.io/gitea/models/issues"
 	repo_model "code.gitea.io/gitea/models/repo"
 	user_model "code.gitea.io/gitea/models/user"
@@ -35,10 +36,14 @@ import (
 )
 
 const (
-	mailAuthActivate       base.TplName = "auth/activate"
-	mailAuthActivateEmail  base.TplName = "auth/activate_email"
-	mailAuthResetPassword  base.TplName = "auth/reset_passwd"
-	mailAuthRegisterNotify base.TplName = "auth/register_notify"
+	mailAuthActivate           base.TplName = "auth/activate"
+	mailAuthActivateEmail      base.TplName = "auth/activate_email"
+	mailAuthResetPassword      base.TplName = "auth/reset_passwd"
+	mailAuthRegisterNotify     base.TplName = "auth/register_notify"
+	mailAuthPasswordChange     base.TplName = "auth/password_change"
+	mailAuthPrimaryMailChange  base.TplName = "auth/primary_mail_change"
+	mailAuth2faDisabled        base.TplName = "auth/2fa_disabled"
+	mailAuthRemovedSecurityKey base.TplName = "auth/removed_security_key"
 
 	mailNotifyCollaborator base.TplName = "notify/collaborator"
 
@@ -561,3 +566,133 @@ func fromDisplayName(u *user_model.User) string {
 	}
 	return u.GetCompleteName()
 }
+
+// SendPasswordChange informs the user on their primary email address that
+// their password was changed.
+func SendPasswordChange(u *user_model.User) error {
+	if setting.MailService == nil {
+		return nil
+	}
+	locale := translation.NewLocale(u.Language)
+
+	data := map[string]any{
+		"locale":      locale,
+		"DisplayName": u.DisplayName(),
+		"Username":    u.Name,
+		"Language":    locale.Language(),
+	}
+
+	var content bytes.Buffer
+
+	if err := bodyTemplates.ExecuteTemplate(&content, string(mailAuthPasswordChange), data); err != nil {
+		return err
+	}
+
+	msg := NewMessage(u.EmailTo(), locale.TrString("mail.password_change.subject"), content.String())
+	msg.Info = fmt.Sprintf("UID: %d, password change notification", u.ID)
+
+	SendAsync(msg)
+	return nil
+}
+
+// SendPrimaryMailChange informs the user on their old primary email address
+// that it's no longer used as primary mail and will no longer receive
+// notification on that email address.
+func SendPrimaryMailChange(u *user_model.User, oldPrimaryEmail string) error {
+	if setting.MailService == nil {
+		return nil
+	}
+	locale := translation.NewLocale(u.Language)
+
+	data := map[string]any{
+		"locale":         locale,
+		"NewPrimaryMail": u.Email,
+		"DisplayName":    u.DisplayName(),
+		"Username":       u.Name,
+		"Language":       locale.Language(),
+	}
+
+	var content bytes.Buffer
+
+	if err := bodyTemplates.ExecuteTemplate(&content, string(mailAuthPrimaryMailChange), data); err != nil {
+		return err
+	}
+
+	msg := NewMessage(u.EmailTo(oldPrimaryEmail), locale.TrString("mail.primary_mail_change.subject"), content.String())
+	msg.Info = fmt.Sprintf("UID: %d, primary email change notification", u.ID)
+
+	SendAsync(msg)
+	return nil
+}
+
+// SendDisabledTOTP informs the user that their totp has been disabled.
+func SendDisabledTOTP(ctx context.Context, u *user_model.User) error {
+	if setting.MailService == nil {
+		return nil
+	}
+	locale := translation.NewLocale(u.Language)
+
+	hasWebAuthn, err := auth_model.HasWebAuthnRegistrationsByUID(ctx, u.ID)
+	if err != nil {
+		return err
+	}
+
+	data := map[string]any{
+		"locale":      locale,
+		"HasWebAuthn": hasWebAuthn,
+		"DisplayName": u.DisplayName(),
+		"Username":    u.Name,
+		"Language":    locale.Language(),
+	}
+
+	var content bytes.Buffer
+
+	if err := bodyTemplates.ExecuteTemplate(&content, string(mailAuth2faDisabled), data); err != nil {
+		return err
+	}
+
+	msg := NewMessage(u.EmailTo(), locale.TrString("mail.totp_disabled.subject"), content.String())
+	msg.Info = fmt.Sprintf("UID: %d, 2fa disabled notification", u.ID)
+
+	SendAsync(msg)
+	return nil
+}
+
+// SendRemovedWebAuthn informs the user that one of their security keys has been removed.
+func SendRemovedSecurityKey(ctx context.Context, u *user_model.User, securityKeyName string) error {
+	if setting.MailService == nil {
+		return nil
+	}
+	locale := translation.NewLocale(u.Language)
+
+	hasWebAuthn, err := auth_model.HasWebAuthnRegistrationsByUID(ctx, u.ID)
+	if err != nil {
+		return err
+	}
+	hasTOTP, err := auth_model.HasTwoFactorByUID(ctx, u.ID)
+	if err != nil {
+		return err
+	}
+
+	data := map[string]any{
+		"locale":          locale,
+		"HasWebAuthn":     hasWebAuthn,
+		"HasTOTP":         hasTOTP,
+		"SecurityKeyName": securityKeyName,
+		"DisplayName":     u.DisplayName(),
+		"Username":        u.Name,
+		"Language":        locale.Language(),
+	}
+
+	var content bytes.Buffer
+
+	if err := bodyTemplates.ExecuteTemplate(&content, string(mailAuthRemovedSecurityKey), data); err != nil {
+		return err
+	}
+
+	msg := NewMessage(u.EmailTo(), locale.TrString("mail.removed_security_key.subject"), content.String())
+	msg.Info = fmt.Sprintf("UID: %d, security key removed notification", u.ID)
+
+	SendAsync(msg)
+	return nil
+}
diff --git a/services/mailer/mail_admin_new_user_test.go b/services/mailer/mail_admin_new_user_test.go
index 603a8b95c..6868e9eb2 100644
--- a/services/mailer/mail_admin_new_user_test.go
+++ b/services/mailer/mail_admin_new_user_test.go
@@ -55,14 +55,14 @@ func TestAdminNotificationMail_test(t *testing.T) {
 		defer test.MockVariableValue(&setting.Admin.SendNotificationEmailOnNewUser, true)()
 
 		called := false
-		defer mockMailSettings(func(msgs ...*Message) {
+		defer MockMailSettings(func(msgs ...*Message) {
 			assert.Equal(t, len(msgs), 1, "Test provides only one admin user, so only one email must be sent")
 			assert.Equal(t, msgs[0].To, users[0].Email, "checks if the recipient is the admin of the instance")
 			manageUserURL := setting.AppURL + "admin/users/" + strconv.FormatInt(users[1].ID, 10)
 			assert.Contains(t, msgs[0].Body, manageUserURL)
 			assert.Contains(t, msgs[0].Body, users[1].HTMLURL())
 			assert.Contains(t, msgs[0].Body, users[1].Name, "user name of the newly created user")
-			assertTranslatedLocale(t, msgs[0].Body, "mail.admin", "admin.users")
+			AssertTranslatedLocale(t, msgs[0].Body, "mail.admin", "admin.users")
 			called = true
 		})()
 		MailNewUser(ctx, users[1])
@@ -71,7 +71,7 @@ func TestAdminNotificationMail_test(t *testing.T) {
 
 	t.Run("SendNotificationEmailOnNewUser_false", func(t *testing.T) {
 		defer test.MockVariableValue(&setting.Admin.SendNotificationEmailOnNewUser, false)()
-		defer mockMailSettings(func(msgs ...*Message) {
+		defer MockMailSettings(func(msgs ...*Message) {
 			assert.Equal(t, 1, 0, "this shouldn't execute. MailNewUser must exit early since SEND_NOTIFICATION_EMAIL_ON_NEW_USER is disabled")
 		})()
 		MailNewUser(ctx, users[1])
diff --git a/services/mailer/mail_auth_test.go b/services/mailer/mail_auth_test.go
new file mode 100644
index 000000000..5346ae0d4
--- /dev/null
+++ b/services/mailer/mail_auth_test.go
@@ -0,0 +1,60 @@
+// Copyright 2024 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package mailer_test
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/models/unittest"
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/optional"
+	"code.gitea.io/gitea/modules/translation"
+	"code.gitea.io/gitea/services/mailer"
+	user_service "code.gitea.io/gitea/services/user"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPasswordChangeMail(t *testing.T) {
+	defer require.NoError(t, unittest.PrepareTestDatabase())
+
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
+	called := false
+	defer mailer.MockMailSettings(func(msgs ...*mailer.Message) {
+		assert.Len(t, msgs, 1)
+		assert.Equal(t, user.EmailTo(), msgs[0].To)
+		assert.EqualValues(t, translation.NewLocale("en-US").Tr("mail.password_change.subject"), msgs[0].Subject)
+		mailer.AssertTranslatedLocale(t, msgs[0].Body, "mail.password_change.text_1", "mail.password_change.text_2", "mail.password_change.text_3")
+		called = true
+	})()
+
+	require.NoError(t, user_service.UpdateAuth(db.DefaultContext, user, &user_service.UpdateAuthOptions{Password: optional.Some("NewPasswordYolo!")}))
+	assert.True(t, called)
+}
+
+func TestPrimaryMailChange(t *testing.T) {
+	defer require.NoError(t, unittest.PrepareTestDatabase())
+
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
+	firstEmail := unittest.AssertExistsAndLoadBean(t, &user_model.EmailAddress{ID: 3, UID: user.ID, IsPrimary: true})
+	secondEmail := unittest.AssertExistsAndLoadBean(t, &user_model.EmailAddress{ID: 35, UID: user.ID}, "is_primary = false")
+
+	called := false
+	defer mailer.MockMailSettings(func(msgs ...*mailer.Message) {
+		assert.False(t, called)
+		assert.Len(t, msgs, 1)
+		assert.Equal(t, user.EmailTo(firstEmail.Email), msgs[0].To)
+		assert.EqualValues(t, translation.NewLocale("en-US").Tr("mail.primary_mail_change.subject"), msgs[0].Subject)
+		assert.Contains(t, msgs[0].Body, secondEmail.Email)
+		mailer.AssertTranslatedLocale(t, msgs[0].Body, "mail.primary_mail_change.text_1", "mail.primary_mail_change.text_2", "mail.primary_mail_change.text_3")
+		called = true
+	})()
+
+	require.NoError(t, user_service.MakeEmailAddressPrimary(db.DefaultContext, user, secondEmail, true))
+	assert.True(t, called)
+
+	require.NoError(t, user_service.MakeEmailAddressPrimary(db.DefaultContext, user, firstEmail, false))
+}
diff --git a/services/mailer/mail_test.go b/services/mailer/mail_test.go
index 54b9c177e..78798bb9f 100644
--- a/services/mailer/mail_test.go
+++ b/services/mailer/mail_test.go
@@ -62,7 +62,7 @@ func prepareMailerTest(t *testing.T) (doer *user_model.User, repo *repo_model.Re
 }
 
 func TestComposeIssueCommentMessage(t *testing.T) {
-	defer mockMailSettings(nil)()
+	defer MockMailSettings(nil)()
 	doer, _, issue, comment := prepareMailerTest(t)
 
 	markup.Init(&markup.ProcessorHelper{
@@ -117,7 +117,7 @@ func TestComposeIssueCommentMessage(t *testing.T) {
 }
 
 func TestComposeIssueMessage(t *testing.T) {
-	defer mockMailSettings(nil)()
+	defer MockMailSettings(nil)()
 	doer, _, issue, _ := prepareMailerTest(t)
 
 	recipients := []*user_model.User{{Name: "Test", Email: "test@gitea.com"}, {Name: "Test2", Email: "test2@gitea.com"}}
@@ -146,7 +146,7 @@ func TestComposeIssueMessage(t *testing.T) {
 }
 
 func TestMailerIssueTemplate(t *testing.T) {
-	defer mockMailSettings(nil)()
+	defer MockMailSettings(nil)()
 	assert.NoError(t, unittest.PrepareTestDatabase())
 
 	doer := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
@@ -160,7 +160,7 @@ func TestMailerIssueTemplate(t *testing.T) {
 		for _, s := range expected {
 			assert.Contains(t, wholemsg, s)
 		}
-		assertTranslatedLocale(t, wholemsg, "mail.issue")
+		AssertTranslatedLocale(t, wholemsg, "mail.issue")
 	}
 
 	testCompose := func(t *testing.T, ctx *mailCommentContext) *Message {
@@ -241,7 +241,7 @@ func TestMailerIssueTemplate(t *testing.T) {
 }
 
 func TestTemplateSelection(t *testing.T) {
-	defer mockMailSettings(nil)()
+	defer MockMailSettings(nil)()
 	doer, repo, issue, comment := prepareMailerTest(t)
 	recipients := []*user_model.User{{Name: "Test", Email: "test@gitea.com"}}
 
@@ -296,7 +296,7 @@ func TestTemplateSelection(t *testing.T) {
 }
 
 func TestTemplateServices(t *testing.T) {
-	defer mockMailSettings(nil)()
+	defer MockMailSettings(nil)()
 	doer, _, issue, comment := prepareMailerTest(t)
 	assert.NoError(t, issue.LoadRepo(db.DefaultContext))
 
@@ -349,7 +349,7 @@ func testComposeIssueCommentMessage(t *testing.T, ctx *mailCommentContext, recip
 }
 
 func TestGenerateAdditionalHeaders(t *testing.T) {
-	defer mockMailSettings(nil)()
+	defer MockMailSettings(nil)()
 	doer, _, issue, _ := prepareMailerTest(t)
 
 	ctx := &mailCommentContext{Context: context.TODO() /* TODO: use a correct context */, Issue: issue, Doer: doer}
@@ -382,7 +382,7 @@ func TestGenerateAdditionalHeaders(t *testing.T) {
 }
 
 func Test_createReference(t *testing.T) {
-	defer mockMailSettings(nil)()
+	defer MockMailSettings(nil)()
 	_, _, issue, comment := prepareMailerTest(t)
 	_, _, pullIssue, _ := prepareMailerTest(t)
 	pullIssue.IsPull = true
diff --git a/services/mailer/main_test.go b/services/mailer/main_test.go
index 399d05ac7..908976e7e 100644
--- a/services/mailer/main_test.go
+++ b/services/mailer/main_test.go
@@ -22,14 +22,14 @@ func TestMain(m *testing.M) {
 	unittest.MainTest(m)
 }
 
-func assertTranslatedLocale(t *testing.T, message string, prefixes ...string) {
+func AssertTranslatedLocale(t *testing.T, message string, prefixes ...string) {
 	t.Helper()
 	for _, prefix := range prefixes {
 		assert.NotContains(t, message, prefix, "there is an untranslated locale prefix")
 	}
 }
 
-func mockMailSettings(send func(msgs ...*Message)) func() {
+func MockMailSettings(send func(msgs ...*Message)) func() {
 	translation.InitLocales(context.Background())
 	subjectTemplates, bodyTemplates = templates.Mailer(context.Background())
 	mailService := setting.Mailer{
diff --git a/services/user/email.go b/services/user/email.go
index 9dc527084..e8725267f 100644
--- a/services/user/email.go
+++ b/services/user/email.go
@@ -12,6 +12,7 @@ import (
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/util"
+	"code.gitea.io/gitea/services/mailer"
 )
 
 // AdminAddOrSetPrimaryEmailAddress is used by admins to add or set a user's primary email address
@@ -163,7 +164,7 @@ func ReplaceInactivePrimaryEmail(ctx context.Context, oldEmail string, email *us
 		return err
 	}
 
-	err = user_model.MakeEmailPrimaryWithUser(ctx, user, email)
+	err = MakeEmailAddressPrimary(ctx, user, email, false)
 	if err != nil {
 		return err
 	}
@@ -190,3 +191,42 @@ func DeleteEmailAddresses(ctx context.Context, u *user_model.User, emails []stri
 
 	return nil
 }
+
+func MakeEmailAddressPrimary(ctx context.Context, u *user_model.User, newPrimaryEmail *user_model.EmailAddress, notify bool) error {
+	ctx, committer, err := db.TxContext(ctx)
+	if err != nil {
+		return err
+	}
+	defer committer.Close()
+	sess := db.GetEngine(ctx)
+
+	oldPrimaryEmail := u.Email
+
+	// 1. Update user table
+	u.Email = newPrimaryEmail.Email
+	if _, err = sess.ID(u.ID).Cols("email").Update(u); err != nil {
+		return err
+	}
+
+	// 2. Update old primary email
+	if _, err = sess.Where("uid=? AND is_primary=?", u.ID, true).Cols("is_primary").Update(&user_model.EmailAddress{
+		IsPrimary: false,
+	}); err != nil {
+		return err
+	}
+
+	// 3. update new primary email
+	newPrimaryEmail.IsPrimary = true
+	if _, err = sess.ID(newPrimaryEmail.ID).Cols("is_primary").Update(newPrimaryEmail); err != nil {
+		return err
+	}
+
+	if err := committer.Commit(); err != nil {
+		return err
+	}
+
+	if notify {
+		return mailer.SendPrimaryMailChange(u, oldPrimaryEmail)
+	}
+	return nil
+}
diff --git a/services/user/email_test.go b/services/user/email_test.go
index 0784b4f80..74f8b8d01 100644
--- a/services/user/email_test.go
+++ b/services/user/email_test.go
@@ -14,6 +14,7 @@ import (
 
 	"github.com/gobwas/glob"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestAdminAddOrSetPrimaryEmailAddress(t *testing.T) {
@@ -163,3 +164,15 @@ func TestDeleteEmailAddresses(t *testing.T) {
 	assert.Error(t, err)
 	assert.True(t, user_model.IsErrPrimaryEmailCannotDelete(err))
 }
+
+func TestMakeEmailAddressPrimary(t *testing.T) {
+	require.NoError(t, unittest.PrepareTestDatabase())
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
+	newPrimaryEmail := unittest.AssertExistsAndLoadBean(t, &user_model.EmailAddress{ID: 35, UID: user.ID}, "is_primary = false")
+
+	require.NoError(t, MakeEmailAddressPrimary(db.DefaultContext, user, newPrimaryEmail, false))
+
+	unittest.AssertExistsIf(t, true, &user_model.User{ID: 2, Email: newPrimaryEmail.Email})
+	unittest.AssertExistsIf(t, true, &user_model.EmailAddress{ID: 3, UID: user.ID}, "is_primary = false")
+	unittest.AssertExistsIf(t, true, &user_model.EmailAddress{ID: 35, UID: user.ID, IsPrimary: true})
+}
diff --git a/services/user/update.go b/services/user/update.go
index 1bdbf13f0..26c90505c 100644
--- a/services/user/update.go
+++ b/services/user/update.go
@@ -14,6 +14,7 @@ import (
 	"code.gitea.io/gitea/modules/optional"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/structs"
+	"code.gitea.io/gitea/services/mailer"
 )
 
 type UpdateOptions struct {
@@ -220,5 +221,13 @@ func UpdateAuth(ctx context.Context, u *user_model.User, opts *UpdateAuthOptions
 		u.ProhibitLogin = opts.ProhibitLogin.Value()
 	}
 
-	return user_model.UpdateUserCols(ctx, u, "login_type", "login_source", "login_name", "passwd", "passwd_hash_algo", "salt", "must_change_password", "prohibit_login")
+	if err := user_model.UpdateUserCols(ctx, u, "login_type", "login_source", "login_name", "passwd", "passwd_hash_algo", "salt", "must_change_password", "prohibit_login"); err != nil {
+		return err
+	}
+
+	if opts.Password.Has() {
+		return mailer.SendPasswordChange(u)
+	}
+
+	return nil
 }
diff --git a/templates/mail/auth/2fa_disabled.tmpl b/templates/mail/auth/2fa_disabled.tmpl
new file mode 100644
index 000000000..3f9d3795c
--- /dev/null
+++ b/templates/mail/auth/2fa_disabled.tmpl
@@ -0,0 +1,15 @@
+<head>
+	<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+	<meta name="format-detection" content="telephone=no,date=no,address=no,email=no,url=no">
+</head>
+
+<body>
+	<p>{{.locale.Tr "mail.hi_user_x" (.DisplayName|DotEscape)}}</p><br>
+	<p>{{.locale.Tr "mail.totp_disabled.text_1"}}</p><br>
+	{{if not .HasWebAuthn}}<p>{{.locale.Tr "mail.totp_disabled.no_2fa"}}</p><br>{{end}}
+	<p>{{.locale.Tr "mail.account_security_caution.text_1"}}</p><br>
+	<p>{{.locale.Tr "mail.account_security_caution.text_2"}}</p><br>
+
+	{{template "common/footer_simple" .}}
+</body>
+</html>
diff --git a/templates/mail/auth/password_change.tmpl b/templates/mail/auth/password_change.tmpl
new file mode 100644
index 000000000..4366b8d72
--- /dev/null
+++ b/templates/mail/auth/password_change.tmpl
@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<html>
+<head>
+	<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+	<meta name="format-detection" content="telephone=no,date=no,address=no,email=no,url=no">
+</head>
+
+<body>
+	<p>{{.locale.Tr "mail.hi_user_x" (.DisplayName|DotEscape)}}</p><br>
+	<p>{{.locale.Tr "mail.password_change.text_1"}}</p><br>
+	<p>{{.locale.Tr "mail.account_security_caution.text_1"}}</p><br>
+	<p>{{.locale.Tr "mail.account_security_caution.text_2"}}</p><br>
+
+	{{template "common/footer_simple" .}}
+</body>
+</html>
diff --git a/templates/mail/auth/primary_mail_change.tmpl b/templates/mail/auth/primary_mail_change.tmpl
new file mode 100644
index 000000000..d17be1988
--- /dev/null
+++ b/templates/mail/auth/primary_mail_change.tmpl
@@ -0,0 +1,14 @@
+<head>
+	<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+	<meta name="format-detection" content="telephone=no,date=no,address=no,email=no,url=no">
+</head>
+
+<body>
+	<p>{{.locale.Tr "mail.hi_user_x" (.DisplayName|DotEscape)}}</p><br>
+	<p>{{.locale.Tr "mail.primary_mail_change.text_1" .NewPrimaryMail}}</p><br>
+	<p>{{.locale.Tr "mail.account_security_caution.text_1"}}</p><br>
+	<p>{{.locale.Tr "mail.account_security_caution.text_2"}}</p><br>
+
+	{{template "common/footer_simple" .}}
+</body>
+</html>
diff --git a/templates/mail/auth/removed_security_key.tmpl b/templates/mail/auth/removed_security_key.tmpl
new file mode 100644
index 000000000..18ae18725
--- /dev/null
+++ b/templates/mail/auth/removed_security_key.tmpl
@@ -0,0 +1,15 @@
+<head>
+	<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+	<meta name="format-detection" content="telephone=no,date=no,address=no,email=no,url=no">
+</head>
+
+<body>
+	<p>{{.locale.Tr "mail.hi_user_x" (.DisplayName|DotEscape)}}</p><br>
+	<p>{{.locale.Tr "mail.removed_security_key.text_1" .SecurityKeyName}}</p><br>
+	{{if and (not .HasWebAuthn) (not .HasTOTP)}}<p>{{.locale.Tr "mail.removed_security_key.no_2fa"}}</p><br>{{end}}
+	<p>{{.locale.Tr "mail.account_security_caution.text_1"}}</p><br>
+	<p>{{.locale.Tr "mail.account_security_caution.text_2"}}</p><br>
+
+	{{template "common/footer_simple" .}}
+</body>
+</html>
diff --git a/templates/mail/common/footer_simple.tmpl b/templates/mail/common/footer_simple.tmpl
new file mode 100644
index 000000000..9011d69d0
--- /dev/null
+++ b/templates/mail/common/footer_simple.tmpl
@@ -0,0 +1 @@
+<p><a target="_blank" rel="noopener noreferrer" href="{{$.AppUrl}}">{{AppName}}</a></p>
diff --git a/tests/integration/user_test.go b/tests/integration/user_test.go
index 20b1cdf97..91de3ece3 100644
--- a/tests/integration/user_test.go
+++ b/tests/integration/user_test.go
@@ -7,6 +7,7 @@ package integration
 import (
 	"fmt"
 	"net/http"
+	"strconv"
 	"strings"
 	"testing"
 
@@ -20,6 +21,7 @@ import (
 	api "code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/modules/test"
 	"code.gitea.io/gitea/modules/translation"
+	"code.gitea.io/gitea/services/mailer"
 	"code.gitea.io/gitea/tests"
 
 	"github.com/stretchr/testify/assert"
@@ -608,3 +610,140 @@ func TestUserPronouns(t *testing.T) {
 		assert.EqualValues(t, userName, "user2")
 	})
 }
+
+func TestUserTOTPMail(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
+	session := loginUser(t, user.Name)
+
+	t.Run("No security keys", func(t *testing.T) {
+		defer tests.PrintCurrentTest(t)()
+
+		called := false
+		defer test.MockVariableValue(&mailer.SendAsync, func(msgs ...*mailer.Message) {
+			assert.Len(t, msgs, 1)
+			assert.Equal(t, user.EmailTo(), msgs[0].To)
+			assert.EqualValues(t, translation.NewLocale("en-US").Tr("mail.totp_disabled.subject"), msgs[0].Subject)
+			assert.Contains(t, msgs[0].Body, translation.NewLocale("en-US").Tr("mail.totp_disabled.no_2fa"))
+			called = true
+		})()
+
+		unittest.AssertSuccessfulInsert(t, &auth_model.TwoFactor{UID: user.ID})
+		req := NewRequestWithValues(t, "POST", "/user/settings/security/two_factor/disable", map[string]string{
+			"_csrf": GetCSRF(t, session, "/user/settings/security"),
+		})
+		session.MakeRequest(t, req, http.StatusSeeOther)
+
+		assert.True(t, called)
+		unittest.AssertExistsIf(t, false, &auth_model.TwoFactor{UID: user.ID})
+	})
+
+	t.Run("with security keys", func(t *testing.T) {
+		defer tests.PrintCurrentTest(t)()
+
+		called := false
+		defer test.MockVariableValue(&mailer.SendAsync, func(msgs ...*mailer.Message) {
+			assert.Len(t, msgs, 1)
+			assert.Equal(t, user.EmailTo(), msgs[0].To)
+			assert.EqualValues(t, translation.NewLocale("en-US").Tr("mail.totp_disabled.subject"), msgs[0].Subject)
+			assert.NotContains(t, msgs[0].Body, translation.NewLocale("en-US").Tr("mail.totp_disabled.no_2fa"))
+			called = true
+		})()
+
+		unittest.AssertSuccessfulInsert(t, &auth_model.TwoFactor{UID: user.ID})
+		unittest.AssertSuccessfulInsert(t, &auth_model.WebAuthnCredential{UserID: user.ID})
+		req := NewRequestWithValues(t, "POST", "/user/settings/security/two_factor/disable", map[string]string{
+			"_csrf": GetCSRF(t, session, "/user/settings/security"),
+		})
+		session.MakeRequest(t, req, http.StatusSeeOther)
+
+		assert.True(t, called)
+		unittest.AssertExistsIf(t, false, &auth_model.TwoFactor{UID: user.ID})
+	})
+}
+
+func TestUserSecurityKeyMail(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
+	session := loginUser(t, user.Name)
+
+	t.Run("Normal", func(t *testing.T) {
+		defer tests.PrintCurrentTest(t)()
+
+		called := false
+		defer test.MockVariableValue(&mailer.SendAsync, func(msgs ...*mailer.Message) {
+			assert.Len(t, msgs, 1)
+			assert.Equal(t, user.EmailTo(), msgs[0].To)
+			assert.EqualValues(t, translation.NewLocale("en-US").Tr("mail.removed_security_key.subject"), msgs[0].Subject)
+			assert.Contains(t, msgs[0].Body, translation.NewLocale("en-US").Tr("mail.removed_security_key.no_2fa"))
+			assert.Contains(t, msgs[0].Body, "Little Bobby Tables&#39;s primary key")
+			called = true
+		})()
+
+		unittest.AssertSuccessfulInsert(t, &auth_model.WebAuthnCredential{UserID: user.ID, Name: "Little Bobby Tables's primary key"})
+		id := unittest.AssertExistsAndLoadBean(t, &auth_model.WebAuthnCredential{UserID: user.ID}).ID
+		req := NewRequestWithValues(t, "POST", "/user/settings/security/webauthn/delete", map[string]string{
+			"_csrf": GetCSRF(t, session, "/user/settings/security"),
+			"id":    strconv.FormatInt(id, 10),
+		})
+		session.MakeRequest(t, req, http.StatusOK)
+
+		assert.True(t, called)
+		unittest.AssertExistsIf(t, false, &auth_model.WebAuthnCredential{UserID: user.ID})
+	})
+
+	t.Run("With TOTP", func(t *testing.T) {
+		defer tests.PrintCurrentTest(t)()
+
+		called := false
+		defer test.MockVariableValue(&mailer.SendAsync, func(msgs ...*mailer.Message) {
+			assert.Len(t, msgs, 1)
+			assert.Equal(t, user.EmailTo(), msgs[0].To)
+			assert.EqualValues(t, translation.NewLocale("en-US").Tr("mail.removed_security_key.subject"), msgs[0].Subject)
+			assert.NotContains(t, msgs[0].Body, translation.NewLocale("en-US").Tr("mail.removed_security_key.no_2fa"))
+			assert.Contains(t, msgs[0].Body, "Little Bobby Tables&#39;s primary key")
+			called = true
+		})()
+
+		unittest.AssertSuccessfulInsert(t, &auth_model.WebAuthnCredential{UserID: user.ID, Name: "Little Bobby Tables's primary key"})
+		id := unittest.AssertExistsAndLoadBean(t, &auth_model.WebAuthnCredential{UserID: user.ID}).ID
+		unittest.AssertSuccessfulInsert(t, &auth_model.TwoFactor{UID: user.ID})
+		req := NewRequestWithValues(t, "POST", "/user/settings/security/webauthn/delete", map[string]string{
+			"_csrf": GetCSRF(t, session, "/user/settings/security"),
+			"id":    strconv.FormatInt(id, 10),
+		})
+		session.MakeRequest(t, req, http.StatusOK)
+
+		assert.True(t, called)
+		unittest.AssertExistsIf(t, false, &auth_model.WebAuthnCredential{UserID: user.ID})
+	})
+
+	t.Run("Two security keys", func(t *testing.T) {
+		defer tests.PrintCurrentTest(t)()
+
+		called := false
+		defer test.MockVariableValue(&mailer.SendAsync, func(msgs ...*mailer.Message) {
+			assert.Len(t, msgs, 1)
+			assert.Equal(t, user.EmailTo(), msgs[0].To)
+			assert.EqualValues(t, translation.NewLocale("en-US").Tr("mail.removed_security_key.subject"), msgs[0].Subject)
+			assert.NotContains(t, msgs[0].Body, translation.NewLocale("en-US").Tr("mail.removed_security_key.no_2fa"))
+			assert.Contains(t, msgs[0].Body, "Little Bobby Tables&#39;s primary key")
+			called = true
+		})()
+
+		unittest.AssertSuccessfulInsert(t, &auth_model.WebAuthnCredential{UserID: user.ID, Name: "Little Bobby Tables's primary key"})
+		id := unittest.AssertExistsAndLoadBean(t, &auth_model.WebAuthnCredential{UserID: user.ID}).ID
+		unittest.AssertSuccessfulInsert(t, &auth_model.WebAuthnCredential{UserID: user.ID, Name: "Little Bobby Tables's evil key"})
+		req := NewRequestWithValues(t, "POST", "/user/settings/security/webauthn/delete", map[string]string{
+			"_csrf": GetCSRF(t, session, "/user/settings/security"),
+			"id":    strconv.FormatInt(id, 10),
+		})
+		session.MakeRequest(t, req, http.StatusOK)
+
+		assert.True(t, called)
+		unittest.AssertExistsIf(t, false, &auth_model.WebAuthnCredential{UserID: user.ID, Name: "Little Bobby Tables's primary key"})
+		unittest.AssertExistsIf(t, true, &auth_model.WebAuthnCredential{UserID: user.ID, Name: "Little Bobby Tables's evil key"})
+	})
+}