Microsoft Exchange Server 2007 may experience problems sending email attachments with file names over 50 characters in length when communicating through certain firewalls. Dušan Košarić, a Slovenian Exchange Server guru, recently posted about this peculiar issue on his blog.
The details seem odd: When sending email messages with attachments through certain types of firewalls, Exchange 2007 would sometimes report the error: 5.5.2 Invalid data in message.
The type of email attachment doesn't seem to matter. The culprit is actually the name of the attachment: file names longer than 50 characters are rejected.
I conferred with Dušan on this issue, and he cited an older version of Symantec's Enterprise Firewall product as being one firewall that produces this problem.
In his words: "I got their firewall error details when this kind of email arrived and we found out there is a problem with CONTENT-DISPOSITION length, which is part of the header that contains attachment information. I must admit that I am still researching why this is happening, because it seems it happens only to email sent from Exchange 2007."
I may be totally off the mark, but my guess is that Exchange 2007 made changes to the way the Content-Disposition header is enumerated. Since this only seems to be happening rarely, I would guess they implemented it a little more rigidly. In turn, this might be causing problems for older firewalls that don't implement the Content-Disposition header quite as scrupulously.
In the meantime, the fix seems simple enough: upgrade the offending firewall. Failing that, make sure that people know not to send email attachments with overly long file names.
About the author: Serdar Yegulalp is editor of Windows Insight, a newsletter devoted to hints, tips, tricks, news and goodies for all flavors of Windows users.
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