Setup CatchAll-Mailbox for specific domain in Exchange

Copper Contributor


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 I tried to introduce a recipient-matches-pattern-condition but that didnt work. 

How can i set this up?



5 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

..except if recipient is member of dynamic group (Group contains all existant Mailboxes


This works for sending a mail to


Now if i introduce a second condition like:

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

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.

Hello there, Initially I had a catch-all rule set up as stated above without the domain-specific rule. However, I've noticed that the rule does not accurately deliver to users that are forwarding to emails outside of the organization.

For example. if an email is sent to email address removed for privacy reasons, if that person has a forwarding rule set up to send to an external email client such as @gmail, then the mail will go through a redirect loop that never actually lands in their mailbox. Is there someway to configure this to allow for the forwarding individuals?