Resolved Gmail has trouble sending Mail to my server

[Compi]

Server operating system version

debian 11.5

Plesk version and microupdate number

18.0.48

I have multiple domains with multiple mailboxes hosted on my server. All of them except one are working fine.

This is the error I get:


I get this error on all mailboxes in this account. All others work. The server hostname uses this domain too but with a subdomain eg plesk.domain.com

I also tested GMX, which works.

 

[Compi]

Here some additional logs. The green one is one one of the working adresses, the red one doesnt work. both are configured the same and i sent the test emails from the same gmail account 30 seconds apart:

 

[Peter Debik]

There is a chance that the reason is a missing or wrong SSL certificate, specifically as you are writing that the affected domain is also the hostname domain. Are you using SNI (individual domain mail server certificates per domain)? Do you also have a valid mail server certificate in place in Tools & Settings > Security > SSL/TLS Certificates > Certificate for securing mail?

 

[Compi]

Let me clarify the hostname thing, I think I wasn't specific enough at the thread beginning, sorry for that.

the server hostname is "plesk.domain.com". Whenever I try to send something to a mailbox ending with @domain.com it doesn't work.
It works for other domains hosted on that same server. It's weird, this isn't my first Plesk installation but the first time I'm encountering this issue.

Do you also have a valid mail server certificate in place in Tools & Settings > Security > SSL/TLS Certificates > Certificate for securing mail?

Yes I think I have

Are you using SNI

Not that I'm aware. It's basically a fresh installation.

 

[Compi]

Gmail just sent me this error:

 

[Kaspar]

View attachment 22073

On the page you have taken this screen shot set the Lets Encrypt certificate as default.

 

[Compi]

Just did that, still the same entry in the logs

 

[Kaspar]

If you go to domain.com > mail settings does it list Lets Encrypt domain.com as the selected "SSL/TLS certificate for mail" pull-down option?

 

[Compi]

Yes it does.

 

[Compi]

Are you using SNI

Is this the correct command?

 

[Peter Debik]

According to some Google results the issue can occur when the MX record of the domain is not pointing to the correct endpoint --> Please verify that the MX record of the domain is pointing to the hostname of the server, not to the subdomain itself (or as an alternative, you can compare the MX records of the two domains in question, the one that works and the one that does not).

 

[Compi]

All is fine and correct... This is super weird.

 

[Compi]

Now I get this error too, wasnt there before:

 

[Peter Debik]

I suggest to contact Plesk Support so that they can look at your server directly.

How to get support directly from Plesk?

Question How to get support directly from Plesk? Answer Lease-type Plesk licenses purchased directly from Plesk running on supported Plesk version include full free support. Perpetual-type license...

support.plesk.com

 

[Compi]

Which is free for the first month, right?

 

[Maarten.]

Which is free for the first month, right?

Yes, it is.

 

[Compi]

The problem is solved. As it turns out, an old MTA-STS policy hosted by the old email provider with a "max_age" of over 180 days was the problem. I now simply made my own MTA-STS policy with the mode "none" and max_age of a day, now emails are slowly starting to arrive again.

Thanks all for your time, tho!

 

[Peter Debik]

Thank you for your feedback, @Compi!