Reply by email

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GitLab can be set up to allow users to comment on issues and merge requests by replying to notification emails.

Prerequisite

Make sure incoming email is set up.

How it works

Replying by email happens in three steps:

1. GitLab sends a notification email.
2. You reply to the notification email.
3. GitLab receives your reply to the notification email.

GitLab sends a notification email

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.

You reply to the notification email

When you reply to the notification email, your email client:

• 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 notification email
• Sets the References header to the value of the Message-ID plus the value of the notification email's References header.

GitLab receives your reply to the notification email

When GitLab receives your reply, it looks for the "reply key" in the following headers, in this order:

1. To header
2. References header
3. Delivered-To header
4. Envelope-To header
5. X-Envelope-To header
6. Received header

If it finds a reply key, it leaves your reply as a comment on the entity the notification was about (issue, merge request, commit...).

For more details about the Message-ID, In-Reply-To, and References headers, see RFC 5322.