Excluding a domain
You can exclude all messages received company wide from specified domains.
In Setup > Company Preferences, on the custom tab, there is a field called "Ignore email address". You can use this option to ignore parts of an email address eg:
1. Ignore message replies sent from within NetSuite - insert @messages.netsuite.com
2. Ignore NetSuite Case emails - insert @cases.netsuite.com
3. Ignore a certain domain xyz.com - insert @xyz.com
4. Ignore email from David Smith at email David.Smith@xyz.com - insert David.Smith@xyz.com