cannot send mail be server does not allow relaying

This most likely means you did not enter your email account user ID and password for the outgoing (SMTP) mail server settings. You need to enter these twice for most email accounts, once for incoming mail and once for outgoing mail.

You have some setting wrong; the server does not believe that you are allowed to send mail through it. You can always try deleting the account, rebooting your iPhone and adding it back.