Setup CatchAll-Mailbox for specific domain in Exchange

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New Contributor

Hi, 

I want to introduce a CatchAll-Mailbox, meaning that all messages sent to non-existant recipients shall be redirected to a specific Mailbox.

 

The basic idea is to introduce a rule that redirects all incoming messages and make an exception for recipients who are member of a Dynamic Group that contains all existing Mailboxes. To prevent exchange from instantly blocking the message and instead process the rules, i set the Accepted Domain to internal relay. 

 

Now i want to make this whole thing domain-specific, meaning it should only apply for unknown recipients of specificdomain.com. I tried to introduce a recipient-matches-pattern-condition but that didnt work. 


How can i set this up?

 

 

4 Replies
There's a "domain is" condition, try that? Or is this for on-premises Exchange?

@Vasil Michev Yeah there is. I also tried it but it doesnt seem to work.

My rule does the following:

 

If sender is outside organisation...

...redirect to catchall@domain.com...

..except if recipient is member of dynamic group (Group contains all existant Mailboxes @domain.com)

 

This works for sending a mail to nonExistant@domain.com

 

Now if i introduce a second condition like:

... and if recipient's domain is 'domain.com'...

the rule never triggers. I assumed that maybe the domain condition only works for users that actually exist, but i also couldn't get it to work with other condition types. Maybe i used it wrong?

 

Can you try with removing the dynamic group condition?

@Vasil Michev doesn't change it, the rule just won't trigger. Keeping the Dynamic group and removing the domain condition instead results in a working rule.

 

Looking in Message Trace i can see that Exchange just let's the mail through. Because the domain is set to internal relay it just tries to redirect the mail to the original recipient, resulting in a loop recognition that blocks on third redirect.