>Which clients are these? In the ISP world (ignoring proprietary clients like AOL) I would guess that >90% of users have Outlook Express. (Notwithstanding the fact that I am sending this from an old copy of Eudora Pro 3.0) Proof that quality is not a prerequisite to success.
The remaining <10% is divided among Outlook, Netscape Messenger, Netscape 6/7, Apple Mail, Entourage, etc. I have been told that Messenger has problems if mail is still downloading when the next scheduled check comes due. Certainly I have seen OE go off into lala land causing hung sessions and maillock problems but I've never figured out the pattern.