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Boundary space gap

Posted on 2005-05-16
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A few of our clients are unable to receive email from us due to the message getting blocked by their spam filter (mail protector).  They have have had several reports from their users that emails from us are being destroyed for containing a vulnerability called "[outlook 'boundary space gap' vulnerability]". Explanation of this vulnerability: "This vulnerability occurs when there is a space or tab in the MIME boundary. This is not RFC compliant, but Outlook will treat it as valid and be able to see a virus that virus scanners will not usually see. There is no legitimate reason for an email to be formed like this."


We are running exchange 5.5 and exchange 2003.  Our IMC is exchange 5.5.  We have no record of any changes causing something like this.  Is there anything that needs to be changed to allow our e-mails to get to this client?  I have also ran virus scans on both servers and multiple clients which all prove negative.  Our outgoing mail is scanned via Clearswift mimesweeper antivirus.  We called clearswift and they said their product does not affect the MIME header at all.  Any ideas?
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Question by:Midabije
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by:Sembee
ID: 14013279
Are you using Word as an email editor? If so try turning it off.

And while you have spoken to Clearswift, that would still be my first thought. Any chance that you can bypass scanning for outbound email?

Simon.
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by:Midabije
ID: 14031197
Plain text went through.  Changing between word as an email editor did not effect the problem.  Any ideas if anything can be configured in Exchange that prevents messages from appearing like they have a virus? (Boundary Gap Vulnerability)
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by:Sembee
ID: 14037612
I haven't found any references to settings in Outlook or Exchange that trigger that message. Lots of references for inbound messages with that vulnerability but nothing about sending.

I still think that it is your AV software causing the problem. Have you tried disabling it or bypassing it to see if messages go through?

What else is on this server that could be scanning the messages? Antispam, anything like that?

Simon.
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by:Midabije
ID: 14047320
once again...we are not receiving this email, a couple of our clients are...their spamfilters are blocking our emails on their end.  Our emails leave our system clean (command interceptor for mime sweeper) and are getting blocked by a few recipients here and there.   Plain text messages however will go through to the same recipeints.  Why would outlook malform the messages when they are sent as HTML or Rich text as opposed to plain text?  Is there a way to fix this or do we have to continue to send messages in Plain text to those clients.  One client is using Declude the other is using Mailprotector.  
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Sembee earned 1500 total points
ID: 14052323
It is not Outlook that is malforming the message. It is something scanning the messages that have been created. This could be either an AV or Antispam scanner or even a combination of the two (if you have both).

The scanner, whether it is your scanner or a scanner somewhere in between is struggling to put a message created by Outlook in HTML or Rich Text back together again after scanning. The plain text messages are fine as the scanner hasn't got to convert the message. The classic cause has been Word as an email editor.

If you have identified which domains are causing the problems then you could use Internet Message Formats setting in Global Settings to force emails sent to those domains to be in plain text.

Simon.
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