I’ve set up a Mailcow server on my domain memighty.in, and it’s generally working fine—I can receive emails from Gmail and Outlook without issues. However, I’m facing a problem where I’m unable to receive emails from certain sources, specifically:

GitHub or any other OTP Emails: When I try to sign up for GitHub or any other service, I don’t receive the OTP email.
SES API Emails: I’m using Amazon SES to send emails to my other domain memighty.com (e.g., user@memighty.com), but these emails are not arriving.
here’s my DNS Records:

Any help would be greatly appreciated! Let me know if you need more details, like Mailcow logs or additional DNS info.

  • DocFraggle replied to this.

  • Well, Github for example even today doesn’t have IPv6 enabled. If this also applies to their mail infrastructure you can guess why no mail arrives at your server 😉
    And I bet there are many other mailserver without IPv6, so they won’t be able to send you mails, too…

    EDIT: I just checked the latest Mailcow release email from today regarding “Release 2025-03b”, it completly went through via IPv4, no IPv6 involved despite my IPv6 address

    EDIT 2: that shouldn’t be flagged as “Best Answer”, just clicked the wrong link

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    Is it intended that you don’t have an A record for your IPv4 entry?

    That could definitley lead to problems

      DocFraggle

      hey it’s intended, since I don’t have a public IPv4 for my server—I’m just using IPv6 , At first, I thought that might be the problem, but then I noticed I’m getting emails from Gmail and Outlook just fine.

      So now I’m wondering, if the missing A record is the issue, how come Gmail and Outlook emails are coming through? And see the Rspamd log table I’ve attached below—the IP address column shows IPv6 for both Gmail and Outlook

        Well, Github for example even today doesn’t have IPv6 enabled. If this also applies to their mail infrastructure you can guess why no mail arrives at your server 😉
        And I bet there are many other mailserver without IPv6, so they won’t be able to send you mails, too…

        EDIT: I just checked the latest Mailcow release email from today regarding “Release 2025-03b”, it completly went through via IPv4, no IPv6 involved despite my IPv6 address

        EDIT 2: that shouldn’t be flagged as “Best Answer”, just clicked the wrong link

        I can confirm that many mail servers around the world do not use IPv6.

        While IPv6 adoption is growing, many mail servers still rely on IPv4. Running a mail server without an IPv4 address can lead to delivery issues, as many receiving servers are not fully compatible with IPv6. For reliable mail delivery, having an IPv4 address is currently essential.

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