I have recently moved an Exchange server from one ISP to a new one. The server configuration has not changed. Since moving to the new ISP, the majority of emails get bounced with an "Undeliverable" message. As of last night, the ISP say the Reverse DNS entry has been added but still they bounce back.
As the ISP is the only change made to the configuration I guess the problem must lie with them but I can't think what.
Suggestions welcome. Thanks