E-mail "Deferred: 452 4.3.1 Insufficient system resources" problems

oml1

Registered
Jan 25, 2013
1
0
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cPanel Access Level
Root Administrator
Hi,
When sending to an established newsletter list just moved to a shiny new cpanel server, the client is complaining of too many bounces.

Many with the error shown below:
...........
Deferred: 452 4.3.1 Insufficient system resources
Message could not be delivered for 12 hours
Message will be deleted from queue
...........

We see to have plenty of resouces and there is no limits set on numbers of sends as far as I'm aware. Any suggestions please?