Hello everyone,
I’ve been encountering some unusual behavior with my Postfix setup lately and could really use some assistance. For the past week, I’ve been noticing strange messages in the Postfix logs, and there seems to be an issue with the transport of mail to .ru domains. However, all other domains (.com to .ru, .ru to .com, Gmail, biz, net, etc.) are functioning correctly.
I’ve thoroughly checked all the A, MX, SPF, and DMARC records, and they are configured correctly. Additionally, the DNS settings appear to be accurate.
Domains related to the mail server can successfully send emails to each other without any issues.
In the Postfix logs, I’m seeing warnings like:
warning: Unable to look up MX host for adc-tech.ru: Host not found, try again
warning: Unable to look up MX host for adcpro.ru: Host not found, try again
And messages like:
4663960EEC: to=<brainpitcher@yandex.ru>, relay=none, delay=8479, delays=8471/0.04/8/0, dsn=4.4.3, status=deferred (Host or domain name not found. Name service error for name=yandex.ru type=MX: Host not found, try again)
and very often like this:
NOQUEUE: reject: RCPT from unknown[185.79.119.4]: 450 4.1.8 <elma-events@avtoban.ru>: Sender address rejected: Domain not found; from=<elma-events@avtoban.ru> to=<nda@adcpro.ru> proto=ESMTP helo=<mail.avtoban.ru>
However, when I use nslookup from the same machine where the Mailcow installation resides, all records resolve perfectly.
I’ve ensured that all necessary ports are open and traceroutes are successful.
Could anyone please provide some guidance on where else I can look into to resolve this issue?
Thank you in advance for your help!