I've had a system running for about a year, and every so often, I get an (incoming) email that just CAN'T get through the system for some vague reason. The error I see is: Nov 1 11:44:00 webhost postfix/smtpd[22189]: NOQUEUE: reject: RCPT from mail-cys01nam02on0089.outbound.protection.outlook.com[104.47.37.89]: 451 4.3.5 Server configuration error; from=<[email protected]12.fl.us> to=<[email protected]> proto=ESMTP helo=<NAM02-CY1-obe.outbound.protection.outlook.com> The weird part is that I can get other emails from other users at the same host, but this vague error from a handful of source emails. Logs dont tell (me) much I guess the only lead I have is "warning: unknown smtpd restriction: "OK"" and I dont begin to know what points at. Have included th main and master in hopes that someone with a bigger brain than might notice what I've done wrong. Nov 1 11:44:00 webhost postfix/smtpd[22189]: connect from mail-cys01nam02on0089.outbound.protection.outlook.com[104.47.37.89] Nov 1 11:44:00 webhost postfix/smtpd[22189]: NOQUEUE: filter: RCPT from mail-cys01nam02on0089.outbound.protection.outlook.com[104.47.37.89]: <[email protected]12.fl.us>: Sender address triggers FILTER amavis:[127.0.0.1]:10026; from=<[email protected]12.fl.us> to=<user@mydomain> proto=ESMTP helo=<NAM02-CY1-obe.outbound.protection.outlook.com> Nov 1 11:44:00 webhost postfix/smtpd[22189]: warning: unknown smtpd restriction: "OK" Nov 1 11:44:00 webhost postfix/smtpd[22189]: NOQUEUE: reject: RCPT from mail-cys01nam02on0089.outbound.protection.outlook.com[104.47.37.89]: 451 4.3.5 Server configuration error; from=<[email protected]12.fl.us> to=<[email protected]> proto=ESMTP helo=<NAM02-CY1-obe.outbound.protection.outlook.com> Nov 1 11:44:00 webhost postfix/cleanup[21915]: 5A4334251F7B: message-id=<[email protected]> Nov 1 11:44:00 webhost postfix/smtpd[22189]: disconnect from mail-cys01nam02on0089.outbound.protection.outlook.com[104.47.37.89] Nov 1 11:44:00 webhost postfix/qmgr[8096]: 5A4334251F7B: from=<[email protected]>, size=976, nrcpt=1 (queue active) Nov 1 11:44:00 webhost postfix/local[22846]: 5A4334251F7B: to=<[email protected]>, orig_to=<postmaster>, relay=local, delay=0.02, delays=0/0.01/0/0.01, dsn=2.0.0, status=sent (delivered to mailbox) Nov 1 11:44:00 webhost postfix/qmgr[8096]: 5A4334251F7B: removed
Let me hop onto this thread as I have had the same problem since two days. At the moment it happens only with facebook.com. This mail is sent every time the problem happens (example): The Postfix log has this: I am completely clueless. All the rest of the system is working nominally, all SSL certificates are up-to-date. Is it a misconfiguration of the facebook mail server? The "OK" looks ok to me at that point, but I don't know the protocol in detail. Any idea?
As you can see, I never got any replies. I've had some success in whitelisting various senders/servers. I dump my logs into splunk, and create alerts looking for "451 4.3.5 Server configuration error;" to correct. Would love to understand the real reason, but after 3 days of beating my head against a wall, I guess I'm happy with the work around.
Thanks for your reply. I have the very strong suspicion that the problem has to do with duplicate postfix whitelist entries. I now remembered that the nuisance started after I had added facebook.com to the Postfix whitelist in ISPConfig. I checked this and found the entry had already been there. After removing the duplicate it seems that the problem has gone.
At least for me, I'm sure that is NOT the cause, as some of these have been from things I've never seen before.
