Mail returned with "smtp;500 5.3.3 Unrecognized command" error - TechRepublic
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March 6, 2009 at 03:24 PM
#2168550
johnaaaaaa20

Mail returned with “smtp;500 5.3.3 Unrecognized command” error

by johnaaaaaa20 . Updated 17 years, 3 months ago

The mail sender recieves an NDR with this error. It seems to repeatedly happen with the same recipients, but maybe 1 out of 50 times it will error, and the rest of the time it works. There are vast numbers of other recipients on the same domain who never get rejected.

This is what the SMTP log on the sending server shows:

67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “xxxx -? TO: SMTP” 500 0

Note the xxxx where normally RCPT would be. Where is this coming from? Note in the full log below that this occurs with more than one recipient:

67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “EHLO -? ourdomain.com SMTP” 250 310
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “MAIL -? FROM: SMTP” 250 40
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 29
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 34
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 36
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 33
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 28
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 37
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 29
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 31
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 30
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 29
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 30
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 30
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 27
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 30
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 33
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 29
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 28
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:53 -0800] “RCPT -? TO: SMTP” 250 28
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “xxxx -? TO: SMTP” 500 0
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 29
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 29
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 31
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 31
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 30
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 29
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 31
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 30
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 32
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 29
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 32
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 31
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 30
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 29
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 32
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 29
67.45.66.1 – ourdomain.com [23/Feb/2009:16:29:58 -0800] “RCPT -? TO: SMTP” 250 39
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “xxxx -? TO: SMTP” 500 0
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “RCPT -? TO: SMTP” 250 32
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “RCPT -? TO: SMTP” 250 30
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “RCPT -? TO: SMTP” 250 30
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “RCPT -? TO: SMTP” 250 28
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “RCPT -? TO: SMTP” 250 27
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “RCPT -? TO: SMTP” 250 28
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “RCPT -? TO: SMTP” 250 35
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “RCPT -? TO: SMTP” 250 33
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “RCPT -? TO: SMTP” 250 32
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “RCPT -? TO: SMTP” 250 37
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “RCPT -? TO: SMTP” 250 32
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “RCPT -? TO: SMTP” 250 32
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “RCPT -? TO: SMTP” 250 44
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “RCPT -? TO: SMTP” 250 27
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “RCPT -? TO: SMTP” 250 40
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:03 -0800] “RCPT -? TO: SMTP” 250 37
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:08 -0800] “xxxx -? TO: SMTP” 500 0
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:08 -0800] “RCPT -? TO: SMTP” 250 44
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:08 -0800] “RCPT -? TO: SMTP” 250 46
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:08 -0800] “RCPT -? TO: SMTP” 250 43
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:08 -0800] “RCPT -? TO: SMTP” 250 43
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:08 -0800] “RCPT -? TO: SMTP” 250 47
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:08 -0800] “RCPT -? TO: SMTP” 250 37
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:09 -0800] “DATA -? <7D1EACA90FF0CB4AA363EFA2E82C23C80256DD84@ourserver.ourdomain.com> SMTP” 250 146
67.45.66.1 – ourdomain.com [23/Feb/2009:16:30:09 -0800] “QUIT -?ourdomain.com SMTP” 240 67

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