Utilizing PMG with Office 365

[john-tapestry]

Hello,

I am attempting to use PMG as a mail gateway for our 365 instance, but when analyzing the tracking center, I receive an error message as follows for any inbound email:



2026-06-26T01:28:36.567425+00:00 proxmox-mail-gateway postfix/smtpd[304985]: connect from mx3.[hidden].com[X.X.X.X]
2026-06-26T01:28:36.862400+00:00 proxmox-mail-gateway postfix/smtpd[304985]: NOQUEUE: reject: RCPT from mx3.[hidden].com[X.X.X.X]: 454 4.7.1 <[hidden]@[hidden]>: Relay access denied; from=<[hidden]@[hidden].com> to=<[hidden]@[hidden].com> proto=ESMTP helo=<[hidden].com>
2026-06-26T01:28:36.889562+00:00 proxmox-mail-gateway postfix/smtpd[304985]: disconnect from mx3.[hidden].com[X.X.X.X] ehlo=2 starttls=1 mail=1 rcpt=0/1 quit=1 commands=5/6

I've checked my DNS records to ensure that the MX server's IP address is listed properly but still nothing. I'm not sure what I'm missing here.

 

[j.theisen]

Hi @john-tapestry

thanks for posting on the forum!

This error message sounds to me as if the incoming mail's recipient is not listed in the relay domain config [1].
Can you please check your current settings and confirm your domain is listed there?

Yours sincerely
Jonas

[1] https://pmg.proxmox.com/pmg-docs/pmg-admin-guide.html#pmgconfig_mailproxy_relay_domains

 

[broadway]

Hello,

I am attempting to use PMG as a mail gateway for our 365 instance, but when analyzing the tracking center, I receive an error message as follows for any inbound email:



2026-06-26T01:28:36.567425+00:00 proxmox-mail-gateway postfix/smtpd[304985]: connect from mx3.[hidden].com[X.X.X.X]
2026-06-26T01:28:36.862400+00:00 proxmox-mail-gateway postfix/smtpd[304985]: NOQUEUE: reject: RCPT from mx3.[hidden].com[X.X.X.X]: 454 4.7.1 <[hidden]@[hidden]>: Relay access denied; from=<[hidden]@[hidden].com> to=<[hidden]@[hidden].com> proto=ESMTP helo=<[hidden].com>
2026-06-26T01:28:36.889562+00:00 proxmox-mail-gateway postfix/smtpd[304985]: disconnect from mx3.[hidden].com[X.X.X.X] ehlo=2 starttls=1 mail=1 rcpt=0/1 quit=1 commands=5/6

I've checked my DNS records to ensure that the MX server's IP address is listed properly but still nothing. I'm not sure what I'm missing here.

Mail DNS hosted in O365?

If so, make sure your reverse DNS/IP is pointing to the PMG location as well. Also, check that you have the IP range from PMG on the scope of entra for trust, MS is picky about mail connections from a lan at your org.