Ok. The first thing I'd try doing is going into Symantec and disabling
scanning of outgoing messages, as it interrupts your SMTP connection in
order to scan the outgoing traffic. If it starts misbehaving then you can
have problems with sending or receiving (depending on what is getting borked
up).
It could also just be one message that's messed up causing other messages to
fail. Try copying all of the messages to your Drafts, then open one at a
time (I'd start with the most recent one, as it's not as likely to be the
problem child) and try sending them again. If they send fine and you get to
one particular one that won't, then you can copy the contents into another
message and try sending it again.
I've often used the following knowledge base article for troubleshooting
this problem. While it's designed for Outlook 2000, I've been able to use
this information in other versions of Outlook as well--particularly when the
PST file gets corrupted.
http://support.microsoft.com/?id=195922
Here's a simpler link that has some of the steps mentioned in the above
article:
http://www.howto-outlook.com/faq/messagestuckinoutbox.htm
