Sending problem

[Ben]

For the last few days, I'll be working online, press Send
on an e-mail, and it just sits in the Outbox. Opening the
e-mail from the Outbox and pressing Send yields the same
result. Pressing Send and Receive on the toolbar has
become the only way to send e-mail. I still have "Send
immediately when connected" selected in my Options. I ran
a virus scan with no results. These e-mails don't have
large attachments or anything else unusual. Any ideas?

Thanks,
Ben