Did you configure your antivirus application to actively scan incoming and
outgoing email? If you did, disable or reinstall the software to omit the
integration with Outlook. This won't compromise your security since your real
time scanner will catch anything it's updated for.
Another thing to verify is that you have your POP3 and SMTP server settings
exactly as advised by your ISP. The settings should be listed on their
website. Make sure you are using the correct authentication methods as
recommended by your internet provider.
