Jan 18, 2005

Spam Filters don’t like Microsoft

A user recently informed us that his campaigns were getting blocked by a certain enterprise spam-filter appliance. We recommended some changes to his content, then it got through fine. Here’s what we changed:

  • Microsoft tags: if you export from Microsoft applications (such as Word), be sure to view your HTML and remove all the extraneous junk that MS likes to throw in.
  • IP Addresses: Don’t refer to IP addresses when you code your links and images.
  • Removing TBODY, THEAD, and TFOOT tags seemed to help (they appear when you use some WYSIWYGs, or export from MS Word)
  • Slimmed down on the use of <STRONG> tags.

It seemed like his problems stemmed from the fact that his email was exported to HTML from MS Word—something we don’t recommend (keep your code lean and mean by using a text editor). We’ve even seen Spam Assassin assign "spam points" to messages  for being "apparently generated from Microsoft Front Page".