Returned Mail - unrecognised command

[riemondi]

Is anyone else having problems with invalid email formats with PHP 4.0.4 and greater? On my 2 machines with PHP 4.0.4> I get bounced messages like the following on about 10% out the messages I send.

The error returned is always "500 5.5.1 unrecognised command oo.com", where "oo.com" is any random part of the host name... for instance it's coming from myhost.foo.com, so it's usually either oo.com or o.com or foo.com... very weird. (btw, obviously I replaced all the domains with fake ones.)

Also, can anyone recommend a good sniffer so I can get to the bottom of this?

Thanks!
Nick

The original message was received at Sun, 17 Jun 2001 21:13:15 -0500
from nobody@localhost

----- The following addresses had permanent fatal errors -----
[e-mail]
(reason: 500 5.5.1 unrecognised command oo.com> SIZE=269)

----- Transcript of session follows -----
... while talking to mail.foo.com.:

MAIL From:<[e-mail]> SIZE=269
<<< 500 5.5.1 unrecognised command oo.com> SIZE=269
554 5.0.0 [e-mail]... Service unavailable
Return-Path: <nobody>
Received: (from nobody@localhost)
by myhost.foo.com (8.11.2/8.11.2) id f5I2DFE14255;
Sun, 17 Jun 2001 21:13:15 -0500
Date: Sun, 17 Jun 2001 21:13:15 -0500
Message-Id: <[e-mail]>
To: [e-mail]
Subject: My Subject
From: [e-mail]

my body goes here.