We have created two new Mail-Enabled Universal Distribution Group in Exchange 2007; can send messages internally to the group and mail is delivered. External address (i.e. Gmail, Yahoo, etc.) return the following;
Google tried to deliver your message, but it was rejected by the server for the recipient domain gtjonline.com by mail.gtjonline.com. [18.104.22.168].
The error that the other server returned was:
550 Requested action not taken: mailbox unavailable
We have seven other UDG's configured exactly the same that work???