This sounds like you need your IT to setup your own mail server in house and well, that's a little beyond what I can detail here but what you are asking for does not appear to be a feature in the mail system you have now.
But it is possible once you get your own mail server.
Bob
I'd like to set it up so that my companies gmail apps for business has a certain domain name blacklisted.
I want outgoing mail to the domain in question blocked for a particular set of employees not everyone.
I'd also like to know how to change the automated message that says it is not permitted to send email to the newly blacklisted domain.
Can anyone help with a step by step how to from the admin panel?
Thanks

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic