Exchange On-Premise and Office 365 Connectors

Occasional Contributor



I have a situation where our company has 2 mailboxes for each employee. 


1 on-premise exchange 2016 and Office 365. 


We are not looking into hybrid or migrating for now, but we want to see mails sent to our Office 365 mailboxes. 


Good example of this is sharing onedrive files, we do not receive notifications in our on-premise mailboxes. They go straight to Office 365. 


What we want to accomplish for now is receive the emails sent to our office 365 mailboxes. 


Would mail flow connectors accomplish this? 





4 Replies

Hello @seyah96 ,

You are in sort of an unsupported scenario, by default when any user from within office 365 sends an email to another office 365 recipient, the emails are routed internally and will be delivered to office 365 mailbox only, even if the MX record for the domain is pointed elsewhere. For regular emails criteria based routing should work :

First create a Distribution group in office 365 with all the mailboxes present in office 365, then as per above article, select condition that if the recipient is part of that DG, route the email via a connector where you have the smart host defined. This should work for regular emails.

For sharepoint sharing invitation emails the behavior has changed a bit over the years, first check where the invite is coming from, whether it shows as coming from a general email address or if it shows coming from the user who shared it. Usually if the person sharing out has an exchange online license assigned it should come from the user. You will have to test if the email so generated is being handled by the CBR rule you setup earlier.

If CBR doesnt workout for you, you might want to consider setting up forwarding on each office 365 mailbox to an external domain alias which is not added in office 365. If you have any domains on-premises which are not added into office 365, you can add an alias for that domain to each on-premises mailbox and setup forwarding on office 365 mailbox. I havent tried it, but a subdomain should workout as well, so you could theoretically add a subdomain alias to an on-premises mailbox; point all the records for the subdomain to on-premises; configure forwarding on each mailbox in office 365; don't add the subdomain in office 365.



@harveer singh 


I will read out on it. 



Hi @seyah96,


not exactly what you want, but there exists a tool that send a notification to an on-site mailbox informing them that they have received an e-mail in online mailbox.

@Victor Ivanidze 


Thank you, I'll check this out