Wrong domain of GitLab's mail server certificate

I wanted to reply to a GitLab issue by mail, but my mail server refused to send it, as the TLS certificate could not be verified. My mail server is configured to strictly verify the respective certificates.

The mail was headed to [...]@gitlab.torproject.org. My mail server queried the MX record of gitlab.torproject.org, but only got a CNAME response, which leads to gitlab-02.torproject.org that points to the right IP addresses. Now my mail server expected a TLS certificate for gitlab.torproject.org, but your postfix provided a certificate for gitlab-02.torproject.org, which my mail server regarded as invalid.

The easiest way to fix this is to add a MX record to gitlab.torproject.org pointing at gitlab-02.torproject.org. That could even help with mail deliverability. Alternatively, you can provide a certificate for gitlab.torproject.org from your mail server just like on the website.

Maybe the test page on internet.nl helps you too.