I'm running windows xp and using outlook 2000 for emails.

Suddenly about 10 days ago emails that I sent stopped arriving at their
destination. I can use the internet and receive emails using the same ISP
account. Emails leave the outbox, but never arrive. I've tried sending
emails to myself with no luck. I've double checked all the email settings
with the ISP's techno dept and all is fine. I've done a system restore to a
time when I know that emails worked, still no luck.

Emails don't always get sent easily. Sometimes it takes 3 or 4 attempts and
sometimes I get a 554 error, but often the emails leave with no problem.

Anyone with any idea what I can do next?

Peter