Domain migration/merge setup prior to changing MX record

[Lauren Daly]

We recently acquired another company who uses G Suite. They will be merging with our company using our email domain. We have created new accounts in O365 and would like to add their existing domain email aliases and group aliases to them before changing the MX record and email flow for their existing domain. The moment we add their domain name to O365 and verify ownership with a TXT DNS record, we lose the ability to email their domain even though the MX record has not been changed. Mail sent from our domain to theirs is immediately undeliverable. We would like everything setup in O365 prior to bringing over mail flow for their domain. How can we accomplish this?

[#2]

Hi Lauren

You have to create a conditional mail routing or forwarding.

You can create a group, put all all new users of that new domain and setup a conditional forwarding pointing to that group.

This article could help you create that https://technet.microsoft.com/en-us/library/jj950234(v=exchg.150).aspx