We have an exchange 2003 server. All inbound mail goes through Postini. Lately, we have noticed that anyone with a Gmail account gets this error when sending us mail:
"Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 530 530 authentication required for relay (#5.7.1) (state 13)."
We have changed nothing on our Exchange server or our internet settings or our router.
I specifically added GMAIL.com to allowed senders on Postini, but still no inbound messages from that domain are working. Yahoo, AOL, Comcast and every other domain I've tried can successfully send mail to our server.
Has anyone else seen this? Any potential workarounds recommended?
Thanks in advance,