Attachment filename filter rules (sophisticated)

Ohlenmacher, Olaf Olaf.Ohlenmacher at colt.net
Wed May 9 13:42:15 IST 2007


Hello,
we drop attachments by filenames extentions. Nowerdays attachment filenames are MIME-coded so that Umlauts and other special characters can be handled in a 7-Bit clean way.

My question:
Are the regular expressions applied to the decoded filenames or are they applied to the encoded filenames.

Background:
I have found binary-UTF-8 encoded attachment filenames in the wild which looks like 

  =?UTF-8?B?ZGFzIGlzdCBlaW4gw6TDtsO8w58gdGVzdGZpbGUgbWl0?=
  =?UTF-8?B?IHNvbmRlcnplaWNoZW4gMTIzNDU2Nzg5MC56aXA=?=

which is a file with the name "das ist ein äöüß testfile mit sonderzeichen 1234567890.zip". 
These binary-coded MIME are not regular, so they can not be parsed from regular expressions.

Best regards,
  Olaf Ohlenmacher

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