Our configuration uses a third-party hosted exchange. Some users will not move to 365 and will continue to receive mail flow through the third party.
Domain has been verified but purposed only for Lync (no Exchange DNS changes). Email forwarding is setup for 365 users so they receive domain.com email through the third party, forwarded to domain.onmicrosoft.com email address. I have confirmed in/outbound mail comes to/from domain.com.
Here's the issue:
Need to roll out to a handful of users at a time. However, as soon as a user has been created in 365 (as newuser@domain.com), email from other 365 users will only send to the 365 webmail/Outlook. Mail forwarding has NOT yet been enabled for newuser in third party.
Question is, how do I configure users in the system without IMMEDIATE email flow being impacted. I would have expected that mail to newuser@domail.com would not be sending to 365 webmail/outlook until mail forwarding was enabled to domain.onmicrosoft.com.