Score:1

Exchange Transport Rule to block combination of recipients?

us flag

Is it possible to create an ETR that blocks certain combinations of recipients? Imagine I have two customers in different domains with similar email addresses. I want to prevent sending to recipient lists that inadvertently mix users from the two domains.

Ideally, I'd block outbound messages with *@domainA.com AND *@domainB.com recipients. Also, blocking outbound messages with [email protected] AND *@domainB.com would be acceptable.

Consider also that the recipients list might be:

TO: [email protected]
CC: [email protected]

Exchange rule predicates seem to be "any" operators. Further, it seems I can't use the same condition twice; it's greyed out on the second condition.

Screnshot of Exchange Transport rule criteria

Score:0
au flag

Is Exchange 2019 or Exchange Online?You could use “ address matches any of these words”, it can be added multiple domains:

enter image description here

bendodge avatar
us flag
Exchange Online. Wouldn't your proposed rule block emails with only a single recipient in either domain?
Score:0
au flag

In Exchange Online, you also could add two domains into the “domain is”: enter image description here

To block outbound messages with [email protected] AND *@domainB.com, you could refer to the following settings:

enter image description here

I sit in a Tesla and translated this thread with Ai:

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