[GH-ISSUE #713] Client host rejected: cannot find your reverse hostname #1060

New issue

Closed

opened 2026-03-14 11:37:12 +03:00 by kerem · 1 comment

kerem commented

2026-03-14 11:37:12 +03:00

Owner

Originally created by @jurgenhaas on GitHub (Jan 22, 2025).
Original GitHub issue: https://github.com/anonaddy/anonaddy/issues/713

When I reply to incoming email through an alias on a custom domain, sometimes that reply doesn't go through with an error message like this:

This is the mail system at host mail.lakedrops.com.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                   The mail system

[<puma.spongy395+flaschenpost=besonderlich.de@genb.de>](mailto:puma.spongy395+flaschenpost=besonderlich.de@genb.de): host
    mail.anonaddy.me[2a00:c6c0:0:108:3::10] said: 554 5.7.1 Client host
    rejected: cannot find your reverse hostname, [2a01:4f8:171:145e::2] (in
    reply to RCPT TO command)

genb.de is my custom domain and mail.lakedrops.com is my mail server. Is there something that needs to be configured on the mail server regarding reverse hostname on IPv6 or is there something else going wrong? If the former, any indication and what exactly would be required?

Originally created by @jurgenhaas on GitHub (Jan 22, 2025). Original GitHub issue: https://github.com/anonaddy/anonaddy/issues/713 When I reply to incoming email through an alias on a custom domain, sometimes that reply doesn't go through with an error message like this: ``` This is the mail system at host mail.lakedrops.com. I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below. For further assistance, please send mail to postmaster. If you do so, please include this problem report. You can delete your own text from the attached returned message. The mail system [<puma.spongy395+flaschenpost=besonderlich.de@genb.de>](mailto:puma.spongy395+flaschenpost=besonderlich.de@genb.de): host mail.anonaddy.me[2a00:c6c0:0:108:3::10] said: 554 5.7.1 Client host rejected: cannot find your reverse hostname, [2a01:4f8:171:145e::2] (in reply to RCPT TO command) ``` genb.de is my custom domain and mail.lakedrops.com is my mail server. Is there something that needs to be configured on the mail server regarding reverse hostname on IPv6 or is there something else going wrong? If the former, any indication and what exactly would be required?

kerem closed this issue

2026-03-14 11:37:18 +03:00

kerem commented

2026-03-14 11:37:23 +03:00

Author

Owner

@willbrowningme commented on GitHub (Jan 22, 2025):

Yes your mail server's IPv6 address does not have reverse DNS as can be seen here.

It looks like your server is with Hetzner, you should be able to set this up in the control panel for your server so that your IPv6 reverse DNS is mail.lakedrops.com. You should also make sure this is set for IPv4 if not already.

All mail servers should have proper reverse DNS setup.

@willbrowningme commented on GitHub (Jan 22, 2025): Yes your mail server's IPv6 address does not have reverse DNS as can be seen [here](https://mxtoolbox.com/SuperTool.aspx?action=ptr%3a2a01%3A4f8%3A171%3A145e%3A%3A2&run=networktools). It looks like your server is with Hetzner, you should be able to set this up in the control panel for your server so that your IPv6 reverse DNS is `mail.lakedrops.com`. You should also make sure this is set for IPv4 if not already. All mail servers should have proper reverse DNS setup.

No labels

bug

pull-request

No milestone

No project

No assignees

1 participant

Notifications

Due date

The due date is invalid or out of range. Please use the format "yyyy-mm-dd".

No due date set.

Dependencies

No dependencies set.

Reference

starred/anonaddy#1060

No description provided.

Rows
Columns