Has anybody else had problems while sending digitally signed S/MIME messages via Courier's SMTP server? It accepts them and delivers them just fine, but it somehow modifies the message body so that the digital signature no longer works and the message shows up as altered--thereby making digital signatures worthless! It's quite aggravating.

The mail client I'm using *is* Outlook, but signed messages go through just fine with other SMTP servers, so it looks like Courier is at fault here.