Sender address rejected: User unknown in virtual mailbox table

studioluminous

I have an issue with my mailcow server rejecting all google workspace account emails regardless of the domain.

Here is the message
`Reporting-MTA: dns; googlemail.com
Received-From-MTA: dns; examplesender@googleworkspace.com
Arrival-Date: Tue, 12 Aug 2025 08:53:29 -0700 (PDT)
X-Original-Message-ID: <53c9c3a2-8ce2-413f-9fc5-fb1b3b570997@Spark>

Final-Recipient: rfc822; myemail@recipient.domain
Action: failed
Status: 5.1.0
Remote-MTA: dns; my.mail.server. (2001:19f0:6001:32c:5400:5ff:fe88:2aa9,
the server for the domain recipient.domain.)
Diagnostic-Code: smtp; 550 5.1.0 examplesender@googleworkspace.com: Sender address rejected: User unknown in virtual mailbox table
Last-Attempt-Date: Tue, 12 Aug 2025 08:53:31 -0700 (PDT)`

Here’s the postfix log entries in the order received:
`CONNECT from [2607:f8b0:4864:20::632]:43093 to [fd4d:6169:6c63:6f77::e]:25

ALLOWLISTED [2607:f8b0:4864:20::632]:43093

connect from mail-pl1-x632.google.com[2607:f8b0:4864:20::632]

Anonymous TLS connection established from mail-pl1-x632.google.com[2607:f8b0:4864:20::632] to my.mail.server: TLSv1.3 with cipher
TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256

NOQUEUE: reject: RCPT from mail-pl1-x632.google.com 2607:f8b0:4864:20::632]: 550 5.1.0 examplesender@googleworkspace.com: Sender address rejected: User unknown in virtual mailbox table; from=examplesender@googleworkspace.com to=myemail@recipient.domain proto=ESMTP helo=<mail-pl1-x632.google.com>

disconnect from mail-pl1-x632.google.com 2607:f8b0:4864:20::632] ehlo=2 starttis=1 mail=1 rcpt=0/1 data=0/1 quit=1 commands=5/7`

This happens with more than one domain and they are separate google workpsace accounts.

I’ve disabled reject_unlisted_sender and reject_unknown_sender_domain in main.cf and master.cf and that fixes the issue but I’m assuming there’s a better fix for this.

esackbauer

Disable all relay checkboxes in your domain config.

studioluminous

None of the relay boxes are checked in that domain so they are already disabled. The GAL(global address list) is checked but I don’t think that’s what you’re referring to.

studioluminous

It would seem that this not only pertains to me receiving email from any and all google workspace accounts but also sending to/replying to them. Similar error persists.

I’ve configured DNS and IP4 and IP6 reverse DNS as well as AA and AAAA records.

Here’s the postfix log entries in the order received for me sending an email:

`connect from ip68-6-110-234.sb.sd.cox.net[68.6.110.234]

Anonymous TLS connection established from ip68-6-110-234.sb.sd.cox.net[68.6.110.234] to connect.studioluminous.net: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256

B4AA747E018: to=myemail@recipient.domain, relay=dovecot[fd4d:6169:6c63:6f77::b]:24, delay=1.8, delays=1.6/0/0.01/0.19, dsn=2.0.0, status=sent (250 2.0.0 myemail@recipient.domain +J8wFEF1nWiqzgEAJ1u1HQ Saved)

B4AA747E018: removed

NOQUEUE: reject: RCPT from ip68-6-110-234.sb.sd.cox.net[68.6.110.234]: 550 5.1.1 examplesender@googleworkspace.com: Recipient address rejected: User unknown in virtual mailbox table; from=myemail@recipient.domain to=examplesender@googleworkspace.com proto=ESMTP helo=<smtpclient.apple>

disconnect from ip68-6-110-234.sb.sd.cox.net[68.6.110.234] ehlo=2 starttls=1 auth=1 mail=1 rcpt=0/1 data=0/1 quit=1 commands=6/8`

Any help on this is much appreciated. Happy to give any other information to assist.

esackbauer

https://gmail.com/postmaster/
Check and register key in your DNS, to indicate google that you are owner of that domain.
Seems not to be a mailcow or setup issue on your side.

studioluminous

Thanks, I had already done that for all domains on my server, but… It turns out there was an entry for each of the domains I was testing in mailcow that had been abandoned and I missed that. Sorry for the wasted time and I appreciate the replies.