troubleshooting Question

email issue - 550 Authentication turned on in your email client

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odewulfFlag for United States of America asked on
ExchangeEmail Protocols
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I really need your help on this one.

For the past day, one of my clients is having issue with email.
people sending them email are getting from time to time a bounce back message with the error: 550 Authentication turned on in your email client.

they have a SBS 2003 server with exchange 2003. we are using mxlogic as spam filter. Mxlogic is telling me that everything is fine on their end. here is what they see witht he bounce back email:
Sender IP:
Spam Score:0.2000003433
Timestamp Event
2009-10-23 12:10:16 MDT Recipient Disposition: [250 Bounce (550 Authentication turned on in your email client.); Mode: normal; Queued: no; Frontend TLS: yes]
2009-10-23 12:10:16 MDT Message Disposition: [250 Message Queued (No RCPTS); Backend TLS: yes; Backend IP:]

we did NOT change anything on the server. I checked the relay and connection setting on the SMTP protocol. I removed the list of allow IP addresses and allow everything but I am still getting the error.
the frustrating part is that some emails go through; some bounce back and some are just not delivered.
If I checked the stmp log and the exchange logs, I don't see any trace of the email reaching the server and being rejected.
Same on the firewall.
I checked the DNS on DNSstuff and everything looks ok
I am not sure what else to check since mxlogic is saying the issue is on our side

any comments will be really appreciated...thanks in advance
bounced back email's header:
 <>: 550 Authentication turned on in your email client.
Included is a copy of the message header:
Received: from unknown [] (EHLO
	by over TLS secured channel
	with ESMTP id (envelope-from <>);
	Fri, 23 Oct 2009 11:51:26 -0600 (MDT)
Received: from unknown [] (EHLO
	by over TLS secured channel
	with ESMTP id (envelope-from <>);
	Fri, 23 Oct 2009 11:51:26 -0600 (MDT)
X-MXL-Hash: 4ae1ed1e516ab9e2-0bd70c173447cb4dcaa69bab5af34e6760b9a52d
Received: from ([fe80::c90e:a505:1a5a:cee5]) by ([fe80::c90e:a505:1a5a:cee5%10]) with mapi; Fri,
 23 Oct 2009 10:51:25 -0700
From: Gaetan Barthelemy <>
To: "" <>
Date: Fri, 23 Oct 2009 10:51:23 -0700
Subject: test 2
Thread-Topic: test 2
Thread-Index: AcpUCW+YimQPO1r3SCCjG+U4lDhDfA==
Message-ID: <>
Accept-Language: en-US
Content-Language: en-US
acceptlanguage: en-US
Content-Type: multipart/alternative;
MIME-Version: 1.0
X-Spam: [F=0.2000000000; CM=0.500; S=0.200(2009101401)]
X-SOURCE-IP: [(unknown)]
X-AnalysisOut: [v=1.0 c=1 a=4/S/ykNBv8gH+knGdNQOtA==:17 a=TwXOz9ExAAAA:8 a]
X-AnalysisOut: [=wac9LyfTAAAA:8 a=6qAeDDmWQYQ1I4ie-AwA:9 a=KXJ4d1vN_F78Gcf]
X-AnalysisOut: [GrOKopNopqfIA:4 a=UHruTiGLuVYA:10 a=gk7TmTEu-qYA:10 a=Srlr]
X-AnalysisOut: [bM6UAaYA:10 a=QS4HSwmSmYQA:10 a=t6PIGNSWQ8YA:10 a=pZ04O51z]
X-AnalysisOut: [LnEA:10 a=UccjYoy8YiYA:10 a=bzFBMl1FJb0A:10 a=yMhMjlubAAAA]
X-AnalysisOut: [:8 a=SSmOFEACAAAA:8 a=cXrfHzxiDRFZiIOIsIwA:9 a=t4DNZMAguns]
X-AnalysisOut: [kPUuuRi8A:7 a=CpWs0z_Bt9sER3dhaZLHv_GKVT8A:4]

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