Non delivery reports are sent by the receiving server. So if a server you are sending to is not configured properly it might hold on to that NDR for a long time – say until it comes back online.
The only thing you can set is enabled or disabled and even that is confusing
It is possible to disable NDR in Exchange. However, there is more then one place to visit if you want to turn off NDRs in Exchange 2007 server. Log on as administrator, and navigate to the Exchange Management Console. It makes most sense to start with the Hub Transport node, remember this role is needed if you send emails to recipients on the same server.
Disable NDR Exchange 2007 Hub Server Turn off NDR Exchange 2007
* Launch the Exchange Management Console
* Expand the Organization Configuration folder
* Click on Hub Transport
* Select Remote Domains (Key point)
* Right-click Default (Tab)
* Click on the Message Format (Tab)
* To turn off NDR, remove the tick on Allow non-delivery reports. (See NDR screenshot to the right)
Note: You can also control ‘Allow delivery reports’ on this tab. These are the normal DSN delivery status notifications.