Multiple senders are receiving this error when sending to our server:
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).
Postini on all inbound mail
Antigen for inbound and outbound
Comcast business class for Internet access
AT&T owns the DNS record.
Recent change - switched from AT&T DSL to Comcast.
Updated MX record with new IP address of router.
Only Hotmail and GMAIL have this problem.
As a test, I opened up Postini for ALL Gmail email and Hotmail, but it didn't fix the the problem.
Any help is greatly appreciated.