Terry writes:
In contrast, I suspect that most enterprises use either
Exchange/MAPI or an IMAP-based solution ...
Both solutions are extremely well suited to intracompany or
intraorganizational e-mail systems in relatively homogenous user
environments. I'd always recommend Microsoft Exchange Server for such
applications over simple SMTP/POP3 solutions, if the bandwidth is not too
restricted.
However, for large, heterogenous, variable-bandwidth networks like the big,
wide Internet, SMTP/POP3 are far superior. The more variables there are,
the simpler a system needs to be in order to have any chance of working
reliably for a large part of the user community. SMTP/POP3 satisfy this
criterion; IMAP generally does not, and Exchange is an exercise in absurdity
in this context.