I have had a Zimbra installation working for about a month when out of the blue, we are getting the error:

HTML Code:
This is the Postfix program at host msp-s2.domain.local.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. ...

...The Postfix program

<name@mail.domain.local>: Host or domain name not found. Name
    service error for name=msp-s2.domain.local type=A: Host not
    found
For all incoming email. Even local email.

In the above error, I have replaced the domain name with 'domain' and username with 'name'.

Note the postfix at msp-s2.domain.local is saying it can't find msp-s2.domain.local yet it knows it is msp-s2.domain.local.

As said above, everything was working. No accounts or domains have been changed recently. A 'dig A msp-s2.domain.local' gives the right answer. 'dig mx msp-s2.domain.local' gives the right answer. 'dig mail.domain.local' responds correctly.

hosts has 'xxx.xxx.xxx.xxx msp-s2.domain.local msp-s2'

One other possible clue, one user's inbox is 2.9GB.

System is
Zimbra 4.0.2 GA
SLES 10.0.1

Resolv.conf is pointing to the internal name server.

Our email is down until this is resolved so any help would be greatly appreciated.