use Perl

  my $msg = new MIME::Lite(
      From => "Dave Smith <dws\@postcognitive.com>",
      ...

and

  my $msg = new MIME::Lite(
      From => "dws\@postcognitive.com",
      ...

produce significantly different email envelopes and headers, and that certain ISPs would filter out the former while letting the latter pass. (An archeological dig into MIME::Lite is on the short list for this week.) (Update: It was an old version of MIME::Lite.)

Then, one of my trusty procmail rules,

   :0
   * ^Content-type:.*html
   Mail/htmlspam

which has faithfully trapped 12,561 HTML-only spams this year, finally serves up a false-positive. And it's a message about scheduling a job interview.

Then, last night, one of my domains gets joe-jobbed, and AOL spits back a handful of bounces before declaring me a spammer.

This week, I think I'll send a real, physical, ink-on-paper letter. It's been a while.