To markiam:
Have you tried rebuilding your Mailbox (select your Inbox, then select "Rebuild" from the Mailbox menu)? I used to run into this problem a lot using IMAP accounts in particular, tho it hasn't happened since the move to Leopard.
To weknowjack:
Your problem sounds completely unrelated to the original poster's, and also kinda confusing. No offense, but it seems there are a few missing pronouns, punctuation marks and participles there. Care to rephrase? Perhaps draw a little diagram of how you want your email to flow in & out? It might help.