[exim] Exiscan MIME anomaly error issues

Hey Tom,

I know that this is undocumented (but ya leaked it out in an email that I
kept :))... I'm using this in my MIME ACL:

       deny    message         = Message contains MIME errors:
$mime_anomaly_text
               condition       = ${if > {$mime_anomaly_level}{0} {yes}{no}}
               logwrite        = Message contains MIME errors:
$mime_anomaly_text

However, it seems that quite a few of my users are reporting that it's
rejecting their email with "Broken BASE64 encoding detected" errors
(severity 2). I'm not entirely sure of their client version, but I wanted
to know if the tests you have are purposefully made strict, or if maybe
they're incomplete so triggering on some false positives?

If you need any examples, let me know and I'll see if I can temporarily
inconvinience a few users and nab you some emails to check out.

Eli.