Is there a way to block emails based on the Global address list.

[tmcmahon33]

Is there a way to block/deny emails that are addressed to unknown recipients in my organization.
For example: JoeBlow@mycompany.com

Joe Blow doesn't exist in my Global address list, therefore the email would get denied/bounced back to the source.

 

[Davetoo]

No, because the email isn't "bad" until it reaches your Exchange server and discovers that there's nobody there with that mailbox, and therefore no way to deliver it, so it generates the unknown mailbox NDR.

I'm Certifiable, not certified.
It just means my answers are from experience, not a book.

 

[tmcmahon33]

....why wouldn't this be a feature in Exchange?

 

[Davetoo]

Not sure I understand your question.

When someone sends an email to user123@yourdomain.com, when user123@yourdomain.com is not a valid emailbox, there's no way for that to be known until the email hits your mail server. Only then can it be determined that user123@yourdomain.com doesn't exist.

What happens then is an NDR is generated, the email to user123@yourdomain.com is deposited into the \badmail folder, and depending upon how you have your server setup, the NDR either goes to the sender, to you, or anyone else you designate.

It's recommended that you not permit NDR's to go to the Internet, because that is a method these spammers use to determine mailbox existance/nonexistance.

To have NDR's go to specified users, modify the setup under your SMTP Virtual Server, Properties-Messages tab.

To stop NDR's from going out to the Internet, modify the setup under Global Settings-Internet Message Format-"Your policy (maybe Default)"-Properties-Advanced.

So I guess maybe the answer to your question, if I do understand it, is that it is a feature of Exchange...sorta.

I'm Certifiable, not certified.
It just means my answers are from experience, not a book.