I get an error message when I try to send emails - it says recipient rejected by the server becuase it does not allow relaying. How do I fix this?

This usually means that you're not on the network of the email service; most providers block sending through their servers from outside their network to prevent their systems from being used for relaying spam. It's usually corrected by putting your email account credentials into the settings for the SMTP server you're using. See:

http://support.apple.com/kb/HT4519

Tap on the primary server and there should be an option to enter authentication credentials. You may need to contact your email provider for the correct settings.

Regards.