Mail flow from OnPrem to Office365

Copper Contributor

Hello everybody,
I have a problem and I would like to ask you who are more experienced.
I have an onpremise exchange server Exchange 2019 CU9 connected to Office365, the MX record sends mail directly to Office365.
For sending mail if the mailbox is on office365 it sends directly via Office365 while if the mailbox is on premise on the exchange server it sends via the exchange server.
I would like to know if it is possible to configure Send connector from onpremise exchange to send via Office365.
I am attaching the screenshots of the on-premise exchange connectors


i hope all it's clear




5 Replies
You should be able to achieve this by configuring your "ExternalMail" send connector with a smart host value that matches your MX record. You could update your hybrid connector to do this, but every time you run the HCW it will update this connector and potentially overwrite the configuration. Ideally you'd create a new send connector and test with a couple of external recipient domains first.
Hi Dan,
my record MX is, i put this record in smart host value?
Yes, that will be the value of the smarthost for the send connector you are using to send outgoing mail (whether it's for a test recipient domain or all domains) via EOP
Hi Dan,
sorry for my delay.
If i have 2 domain (mydomain1 and mydomain2) i need to add in smarthost 2 value? For example and

Thx in advance
You should only need to configure the one smarthost value. This configuration is just so that outgoing mail goes to the correct EOP instance. If you have two custom domains added to your tenant, the values you mention above both point to the same EOP instance anyway. It won't hurt to add both, but it won't provide any extra redundancy