Hello all, I've been dealing with this issue since last night when I started to test the sending and receiving from several email providers to see if the server is working well. I have two domains in the server, the one from server domain, and another. If I send it to the first domain from Gmail I receive it on the mailbox for the first domain, but I cannot receive on the second, this is driving me crazy! On Second domain: So M$, Proton, and Others, I can receive emails sent by their email servers but when sending from GMAIL, not even get a connection to the server. I can send it to GMAIL and I can see that it says all email validation settings are ok, but if i reply I get nothing. All DNS settings are in place and working, including SPF, DKIM, and DMARC. Since this is dockerized it seems something is blocking the incoming from GMAIL to second domain?, but this does not make any sense. Thanks in advance. JG

Hello all, So the mystery has been solved !! For future reference, I thought I had taken all the steps needed to move my email domain to a new server. I raised the question here because is a new software for me, and this looked very strange and weird, but in fact, was a security measure implemented, and in fact, it does work as needed. The issue is related to the MTA-STS policy implemented on my MIAB setup, which 'enforces' the use of the email server declared on the policy. This will take 7 days to disappear so, but this is a non-PROD domain, that mainly receives status from other servers. The question is 'Why is Gmail the only provider respecting this policy?' For the future ... Best regards, and many thanks to all. Jorge Gomes

@"DocFraggle"#p13519 All checks, also if I switch to my old server, within 5 mins I receive the test email from google. I have reverted the snapshot to yesterday when I only have 1 domain: - switched the MX to MC and sent an email, i received a 'no relay allowed', correct since I dont have it on the server; - created the domain and sent it again ... no connection whatsoever ... Keeps weird...

Easiest way: via the mailcow GUI -> Logs -> Rspamd [upl-image-preview url=https://community.mailcow.email/assets/files/2024-02-16/1708090235-126169-image.png]

New setup and I cannot receive any incoming emails from GMAIL Servers

KaiserN

is the 2nd domain an alias?

did you receive an error message from google why the email could not be sent?

jasgggit

Hello and thank you for the reply.

And no, it’s not an alias, and no no messages or NDR’s from Google.
It doesn’t even appear the connection on the Postfix log.
I just switched the MX record to my other mail server, and all messages arrived … so it’s not Google not sending to my domain …

This is very strange!.

KaiserN

check your DNS settings again

if there is no connection attempt and the other domain works fine its sounds like a DNS/TTL issue or something like this.

jasgggit

Yes, it does, but all the DNS are ok , and I see no TTL issue if I switch to the other server, MX record in CF has a 1 min TTL, and yes it’s not that TTL you referring to, but just saying I can switch MX servers quickly …

Any ideas on how to troubleshoot this?

Thanks.

DocFraggle

Did you switch your MX record from the old/2nd server to mailcow? Did you check your old/2nd MX if the Google MX still sends it’s mails to this host? It could be that Google takes it’s time to update it’s DNS cache despite of the low TTL

jasgggit

DocFraggle

All checks, also if I switch to my old server, within 5 mins I receive the test email from google.

I have reverted the snapshot to yesterday when I only have 1 domain:

switched the MX to MC and sent an email, i received a ‘no relay allowed’, correct since I dont have it on the server;
created the domain and sent it again … no connection whatsoever …

Keeps weird…

yablock0

I would check rspamd history. Had similar problems with gmail being blocked by it for some reason. I had to raise spam thresholds in Configuration tab. I’m still figuring things out.

jasgggit

yablock0
But its beeing blocked for a specific domain?
If I send it to the other domain it comes thru…

Nedd to do so … neves used rspamd … need to figure it out.
Thanks.
JG

DocFraggle

Easiest way: via the mailcow GUI -> Logs -> Rspamd

jasgggit

DocFraggle
Thanks, but thats not it … reviewing all logs …

I can’t receive GMAIL sent email for this domain in particular …

This is driving me crazy …

esackbauer

Check once again your reverse DNS (PTR) records, for both IPv4 and IPv6, they must match in both directions and have correspondig A records.

jasgggit

esackbauer

All good, since as I said I can receive emails on this domain from another providers,
Not Gmail…

PTrs are corret, no IPV6 configured thou.

Thanks.

So, I m reinstalling the server ….

I m going to setup another Mailserver software to see if it happens with IT ..
Made a snapshot so will be reversible …

I ll keep you posted…. I was enjoying this Mailserver software thou.

I’m familiar with Zimbra and MIAB deployments so … lets see.

Thanks for your quick replies.

So, I m reinstalling the server ….

I m going to setup another Mailserver software to see if it happens with IT ..
Made a snapshot so will be reversible …

I ll keep you posted…. I was enjoying this Mailserver software thou.

I’m familiar with Zimbra and MIAB deployments so … lets see.

Thanks for your quick replies.

jasgggit

Ok, so bad news for me …

This issue happens with my quick setup of a MIAB server …

For some reason I can’t understand, I can’t receive emails from Gmail to my domain, but can to the others I setup on this same server!, this is only happening with Google to this server and this domain.

Reverting to mailcow as this seems not related to it.

Thanks guys going to check with Google, wish me luck …

Regards.
JG

DocFraggle

Did you ever check your new server with MXToolbox?

https://mxtoolbox.com/SuperTool.aspx?action=smtp%3Afqdn.of.your.mail.server

Maybe it gives you a clue

jasgggit

DocFraggle

Yes, I did all of that and more…
I’m not a beginner on this road, only on this mailcow software.
For some reason Gmail, or Contabo, doesn’t like my domain to receive email …on this special domain.

I have deleted the domain from the server and I’m going to move on, as it seems working ok.
This was a test domain, so let’s try with some production domains.

Thanks, guys, but this indeed is very weird, and on so many years deploying mail servers, never encountered such an issue, but Google is Google…

Regards.
JG

DocFraggle

Sure, no problem! For us it’s very hard to help you without knowing all the details of your mailcow… all we can give are suggestions and hints

jasgggit

DocFraggle

And I do understand perfectly that, but I just installed the server using the documentation, no tweaks, as I’m beginning to understand all this new software.

I’m well around Docker and Linux, but my question here was because I didn’t know the software and it could be something I was doing wrong.

But as I said, a quick deployment of an MIAB just replicated the issue, so it’s not Mailcow-related, but indeed seems to be Gmail or other external factors that I cannot find a clue about…

Many thanks for your quick reply, as I’m going to keep using the mailcow for a production server, so let’s see how it goes. I did like the way it’s implemented.

If some of you have any hints on how to harden it, maybe using CSF firewall, I did find some docs for it, but for now I’m not using it.

And also I have a problem with the internal server domain and the one on the docker …
It keeps nagging that the server is using the same name and that some users (those are service users) are not in the virtual list…

But this seems to be another topic …

Regards.
JG

DocFraggle

jasgggit And also I have a problem with the internal server domain and the one on the docker …
It keeps nagging that the server is using the same name and that some users (those are service users) are not in the virtual list…

What do you mean? What / which service is “nagging”?

jasgggit

DocFraggle

Mainly these types of things:

postfix-mailcow-1 | Feb 16 18:20:04 ae85e1190d9a postfix/smtpd[1770]: NOQUEUE: reject: RCPT from unknown[172.22.1.1]: 550 5.1.1 root@box.example.com: Recipient address rejected: User unknown in virtual mailbox table; from=smmsp@box.example.com to=root@box.example.com proto=ESMTP helo=<box.example.com>
postfix-mailcow-1 | Feb 16 18:20:04 ae85e1190d9a postfix/smtpd[1770]: NOQUEUE: reject: RCPT from unknown[172.22.1.1]: 550 5.1.1 smmsp@box.example.com: Recipient address rejected: User unknown in virtual mailbox table; from=<> to=smmsp@box.example.com proto=ESMTP helo=<box.example.com>
postfix-mailcow-1 | Feb 16 18:20:44 ae85e1190d9a postfix/smtpd[1770]: NOQUEUE: reject: RCPT from unknown[172.22.1.1]: 550 5.1.1 postmaster@box.example.com: Recipient address rejected: User unknown in virtual mailbox table; from=<> to=postmaster@box.example.com proto=ESMTP helo=<box.example.com>

and this too …

postfix-mailcow-1 | Feb 16 11:20:04 ae85e1190d9a postfix/smtp[410]: warning: host box.example.com[x.x.x.x]:25 greeted me with my own hostname box.example.com
postfix-mailcow-1 | Feb 16 11:20:04 ae85e1190d9a postfix/smtp[410]: warning: host box.example.com[x.x.x.x]:25 replied to HELO/EHLO with my own hostname box.example.com
postfix-mailcow-1 | Feb 16 11:20:04 ae85e1190d9a postfix/smtp[410]: 9DC00E60133: to=root@box.example.com, relay=box.example.com[x.x.x.x]:25, delay=3.4, delays=3.3/0.03/0.01/0, dsn=5.4.6, status=bounced (mail for box.example.com loops back to myself)
postfix-mailcow-1 | Feb 16 11:20:04 ae85e1190d9a postfix/smtpd[408]: disconnect from unknown[172.22.1.1] ehlo=1 quit=1 commands=2
postfix-mailcow-1 | Feb 16 11:20:04 ae85e1190d9a postfix/cleanup[409]: EF9E9E60135: message-id=20240216102004.EF9E9E60135@box.example.com
postfix-mailcow-1 | Feb 16 11:20:04 ae85e1190d9a postfix/bounce[412]: 9DC00E60133: sender non-delivery notification: EF9E9E60135
postfix-mailcow-1 | Feb 16 11:20:04 ae85e1190d9a postfix/qmgr[373]: EF9E9E60135: from=<>, size=3763, nrcpt=1 (queue active)
postfix-mailcow-1 | Feb 16 11:20:04 ae85e1190d9a postfix/qmgr[373]: 9DC00E60133: removed

box - is the server name, and it’s assuming that there is a mail domain starting with box …

I’ve created an alias for domain ‘box.example.com’ but doesn’t solve it …

DocFraggle

Which OS is running on your server? Is there another mail server running outside of docker (which should be stopped and disabled or moved to another port than 25 beforehand)? smmsp seems to be a user used by sendmail

jasgggit

DocFraggle

Ubuntu 22.04 and yes there was sendmail installed, actually be me, by mistake …
But it’s removed now … shouldn’t be causing this ..

I’m going to recheck !! Thanks