0x800CCC79

The message could not be sent because one of the recipients was rejected by the server.

Make sure you are connected to the Internet at the time the error occurs.

Double-check the recipient address.

If there are several emails in your outbox, or if there is a large one, try removing some of them.

Try sending an email to yourself.

If you still get the error, make sure your email account settings are correct. The reply to address should be empty. Try reconfiguring your email account.

This could be an issue with a home network of more than one computer.