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---
stage: Plan
group: Certify
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info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
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---
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# Reply by email **(FREE SELF)**
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GitLab can be set up to allow users to comment on issues and merge requests by
replying to notification emails.
## Requirement
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Make sure [incoming email ](incoming_email.md ) is set up.
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## How it works
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Replying by email happens in three steps:
1. GitLab sends a notification email.
1. You reply to the notification email.
1. GitLab receives your reply to the notification email.
### GitLab sends a notification email
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When GitLab sends a notification and Reply by email is enabled, the `Reply-To`
header is set to the address defined in your GitLab configuration, with the
`%{key}` placeholder (if present) replaced by a specific "reply key". In
addition, this "reply key" is also added to the `References` header.
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### You reply to the notification email
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When you reply to the notification email, your email client:
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- Sends the email to the `Reply-To` address it got from the notification email
- Sets the `In-Reply-To` header to the value of the `Message-ID` header from the
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notification email
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- Sets the `References` header to the value of the `Message-ID` plus the value of
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the notification email's `References` header.
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### GitLab receives your reply to the notification email
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When GitLab receives your reply, it looks for the "reply key" in the
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following headers, in this order:
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1. `To` header
1. `References` header
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1. `Delivered-To` header
1. `Envelope-To` header
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If it finds a reply key, it leaves your reply as a comment on
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the entity the notification was about (issue, merge request, commit...).
For more details about the `Message-ID` , `In-Reply-To` , and `References headers` ,
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see [RFC 5322 ](https://tools.ietf.org/html/rfc5322#section-3.6.4 ).
