A. Are you selecting the pop account as the sending acct? Unless you choose it at the time you compose the message, it will go out through the default acct, which is usually the exchange acct. Replies and forwards should use the acct that the message arrived on.
B. Rules work just fine on exchange acct. It's possible the slow connection is causing a problem as rules don't run until the message is downloaded in full.
The connection speed is likely the cause of the slow update.
Gerhard Fiedler wrote on Sat, 03 January 2009 21:22
The only problems I'm really having are that A) it doesn't seem to be
possible to prevent the Exchange account from delivering email and/or B)
that Outlook's filters don't work on the email that is delivered through
the Exchange account. (They work though if I run them manually over the
emails that the Exchange account placed in my Inbox, so the filters seem
to be ok.) If I could solve either of these, my setup would work.
(A nice thing would also be if it didn't take as much as 20 seconds to
save my currently 12 or so "client-only" filters... Hard to imagine what
it has to talk to the Exchange server for that long about supposedly
"client-only" filters 
Thanks,
Gerhard
--
Diane Poremsky [MVP - Outlook]
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