MS Exchange 2003 5.3.3 Unrecognized command
Posted on 2010-11-17
I have a few domains that I am unable to send email to. These were email addresses that I was sending to on a regular basis, until recently when I now get the following bounceback message:
Your message did not reach some or all of the intended recipients.
Sent: 10/28/2010 9:57 AM
The following recipient(s) cannot be reached:
firstname.lastname@example.org on 10/28/2010 9:59 AM
A critical function required for the transfer or delivery of the message was not supported by the originator of the report
<mail.capitalgazette.com #5.3.3 smtp;500 5.3.3 Unrecognized command>
Following normal SMTP troubleshooting results in the following:
telnet mail.somewhere.com 25
220 **** etc etc...
250 mail.somewhere.com Hello [188.8.131.52]
MAIL FROM email@example.com
250 2.1.0 firstname.lastname@example.org....Sender OK
250 2.1.5 email@example.com
500 5.3.3 Unrecognized command.
This happens on all the domains with this particular bounceback, they all fail at the DATA command.
So far I have tried... adding SPF record, PTR record, correcting the FQDN (it was incorrect previously). Nothing had any affect. I am using Exchange 2003 for outgoing mail, with a Barracuda spam filter set for inbound mail only. One possible common theme is that at least two of the domains I have problems with have "upgraded" to Exchange 2010 (from older versions of Exchange) around the time this started happening.