Mail flow/transport rules and subaddresses

New Contributor

I'm reaching the limits of my patience trying to solve something relatively simple in concept and am turning to the community to point me in the right direction.


Here's the problem: When an email hits our Exchange server (Exchange Online) from outside the domain and the recipient's address contains a particular subaddress tag I need that email BCCd to a shared inbox.


I've tested a variety of mail flow/transport rules in an attempt to solve this, and I can get them to fire if using some other criteria (ex. if a specific word is found in the subject line), but never as I outlined above. An example of one such failed rule:


Thoughts, tips, tricks? Any help would be much appreciated. Thanks in advance.

4 Replies
Try using "The message > To or CC box contains" condition instead.

@Vasil Michev Thanks for the reply. I tried as you suggested and it works. However, if I'm not mistaken, this method doesn't make use of the +tag (subaddressing) as a condition for triggering the rule. Is that correct?


Just for some added clarity, I'd like the rule to fire when the in-domain recipient address looks like: marketing+outreach AT domain.tld or JoeBlank+outreach AT domain.tld  ... really any time the "outreach" subaddress is used. Is that doable?


Thanks again!

Use the "match" condition then, that allows you to use wildcards.
Thanks again, Vasil. I appreciate your help!

On that note, your suggestions prompted me to try a different angle altogether. Instead of pursuing subaddressing, I opted to create aliases. It's more work and ultimately less flexible, but the results are encouraging.

Here's a quick rundown:
• An alias was created for each address the rule should act on using the same pattern as shown above. An example of that would be: marketing.outreach AT domain.tld (using "." or other accepted character in place of "+").
• Incoming messages would never show the alias in the To field of the message itself. However, they are captured/displayed in the message header. I adjusted the rule accordingly. Here's what that looks like:

While I'm hoping one day to be able to leverage subaddressing in the same way, I think we've arrived at a viable solution to the problem.

Thanks again for your help!