We have sudenly started having a problem with all mail being deferred. The server has been running fo quite a while with no issues...this seems to have just spontaneously happened. Here's an example of a message being deferred in the log (email address changed of course):

Jun 22 08:28:12 srv161 postfix/qmgr[16714]: B23D11D351BB: to=<hidenaddress@somedomain.com>, relay=none, delay=1182, status=deferred (delivery temporarily suspended: conversation with 127.0.0
.1[] timed out while sending end of data -- message may be sent more than once)

I havent seen any errors in any of the logs (zimbra, catalina, etc). Upgraded to the latest version of zcs to see if the problem corrected itself. I made a change in teh host file to emsure that the domain pings to localhost:

[zimbra@srv161 ~]$ ping ai.4ph.com
PING localhost.localdomain ( 56(84) bytes of data.
64 bytes from localhost.localdomain ( icmp_seq=0 ttl=64 time=0.060 ms

DNS resolution is turned off in both server and global settings.

We have about 4500 messages all failing like this. Basically nothing is getting through.

Any help would be greatly appreciated.