Okay phew WOW this has been a learning adventure.
If you have AT&T and are having trouble relaying than this thread is for you:
So I've been on and off the phone with my ISP AT&T for days now at this...
I got this email not too long ago from them, this is the email verbatim:
Dear AT&T Internet Services Member,
We have received questions regarding the following error message which is received by customers when they send e-mail using a non-verified e-mail address:
“Unable to send the message. Please verify the e-mail address in your account properties. The server responded: 553 From: address not verified.”
If you have received this error message, you will continue to receive it for emails sent with a non-verified address until you verify your Yahoo! email address or any other non AT&T email addresses (e.g., firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, etc.). Verification instructions are available on the AT&T Help site http://helpme.att.net/article.php?item=11646. If you have already verified your non AT&T email address and are no longer receiving the 553 error message, please disregard this email.
Thank you for your attention to this matter as we work to improve your Internet service. Our goal continues to be to make you a very satisfied customer. If you are experiencing any issues and would like to speak to a customer support representative, please contact us at 1-877-722-3755.
AT&T Internet Services
Yahoo! is a registered trademark of Yahoo! Inc.
© 2008 AT&T Intellectual Property. All Rights Reserved. AT&T and the AT&T logo are trademarks of AT&T Intellectual Property.
If you visit the site that they link to in the email, it gives detailed instructions on how to set up a "verified" mail account by hand, one at a time, for each email address you would like to relay through their servers.
That part sucks. The fact that if I want to host websites at my house through my crappy DSL service, then every single email address I also want to host must be "verfieid" (they send you a verification code to the email address you register with them and you have to re-type it in their prompt).
So there it is, ISPConfig has worked great from the start, in fact, doing everything this site has told me has worked absolutely perfectly each time. The entire time emails were wonky because AT&T are absolute spam nazis.
I'd just like to give a big thanks to the guys here who write the tutorials and who answer these posts. you guys rule. You have completely renewed my interest in Linux. /sap