[TriLUG] OT: mail servers corrupting our attachments

[Christopher L Merrill]

I guess this is OT, since OUR servers (BSD and Linux) do NOT have this
problem.  We send out license keys to our customers via email.  The keys
are encrypted files (i.e. binary).  We've always received reports of the
license keys arriving corrupted.  But the reports are becoming more and
more frequent.  When we zip the key and resend it (manually), the keys
always get through.

Firstly, I don't understand why the servers are corrupting any attachments.
I could understand if they were simply stripped...by malware filters, for
instance.

I surmise that if the servers were actually inspecting the contents of
the files, both look like binary files, so both should get munged.  But
since only the non-.zip files get munged, the servers are looking at
either the first few bytes to identify Zip files (PK...) or they are
looking at the file extensions.  Since I've heard people recommend
renaming files to *.zip to get past mail filters, I suspect that some
or all of these servers are looking at file extensions.


So finally...my questions:

Is it common for mail servers or malware scanners to use the filename
extension to determine the attachment type?

If we simply renamed our licence keys to *.zip, would we cut down the
frequency of our corrupted key compaints?

Any other suggestions?


TIA,
C



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Chris Merrill                  |  http://www.webperformanceinc.com
Web Performance Inc.

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