If they're stuck in the outbox, retype your username and password for the SMTP server on the Servers tab in the account's properties and check/send. Also, make sure the port is 465 or 587 with TLS checked.
On the outgoing tab in the account's properties, make sure "queue messages" is not checked.
If you have an anti-virus with an email scanner, turn the email scanner off.
Check your firewall settings.
Check for spyware and make sure nothing is enabling a system proxy, hijacking your windows HOSTS file or hijacking your DNS settings.