SMTP communication problem, 521 Syntax error - Exchange Server 2003
Posted on 2009-04-23
Recently, we did a huge server move which included a change in public IP of our E-mail server, even after registering our reverse DNS, we had issues sending to AT&T. I posted an E-mail to AT&T postmaster requesting an unblock for this errorcode.
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<exchange2.broward-workforce.org #5.5.0 smtp;521 Syntax error>
AT&T postmaster has come back to tell me that theyre not blocking our e-mails, which leads me back to the 521 Syntax Error, Ive never seen anything like that in an error code before on the 5.5.0 error, what perhaps could be the culprit in this issue?