451 4.7.1 Service unavailable - try again later (in reply to end of DATA....
Server version: 7.1.2_GA_3268.UBUNTU10_64 UBUNTU10_64 FOSS edition
We are getting some emails returned as undeliverable by our server with the following message,
My first guess was that the emails had unusually long attachements that was causing a timeout before the DATA section had completed. However people are reporting that their emails to us are bounced with a size less than 2MB.
host mail.our-zimbra-server-domain.com[xx.xx.xx.xx] said: 451
4.7.1 Service unavailable - try again later (in reply to end of DATA
I put a watch on the zimbra.log for anything with the word "timeout" in it. There are lots of messages like...
...and a few like...
May 14 17:27:48 mail postfix/smtpd: timeout after END-OF-MESSAGE from localhost[127.0.0.1]
However none of these timeout messages involves one of the IP addresses involved in a sender who has confirmed they were getting their email bounced from us. There doesn't seem to be anything obvious in the logs when it happens, although I am still searching around the date/time of the rejections.
May 14 05:57:31 mail postfix/smtpd: timeout after DATA (7008 bytes) from unknown[.....
Simply egrepping for "[^0-9]451[^0-9]" doesn't show anything except an unlrelated mention of the number "451".
Our Zimbra server is running on a VSpere 5/SAS/SATA environment on a Dell 2950.
I would appreciate some ideas on what might be causing these timeouts and where they would be reported if not in zimbra.log.