Fix Mail Server On Ubuntu

I am getting the following error on all my domains after changing the domain information on my server to match my new root domain. The server runs exim, dovecot, and squirrelmail. Message not sent. Server replied: Requested action not taken: mailbox unavailable 550 relay not permitted Please write "mail server" in your bid so I know you've read this. Please bid your true bid, I don't want to negotiate after the fact. I will need it all set up to point at the correct ptr, and with the error resolved for all of the domains (the error only occurred today, all of the domains could send mail before I made said changes.)