Setup
Exchange 2007 on a single server; Postini for mail filtering.
Accepted domains:
- mycompany.co.uk
- mycompany.fr
- mycompany.de
Symptoms
Staff from the French office are finding that some (not all) of their outgoing messages are getting stuck in the queue and giving "4.5.0 No recipient succeeded" when retried. At each retry Exchange sends the sender a message containing: ""Postini #550 MTA inaccessible for too long for domain:xxxx.fr - psmtp" (where xxxx is the recipient company name).
After 48 hours Exchange stops trying and sends an NDR.
All the stuck messages are to "xxx.fr" domains. We're not having this problem for any of our .co.uk or .de staff. What's more, the French staff can send successfully to some .fr email addresses, and to other domains (e.g. .com).
This began in recent weeks but I can't think of anything that changed on our...