We have an aquisition for another company we need to move into our tenant. They currently have 365 as well
us- tenant 1 with companya.com email addresses
their - tenant 2 companyb.com email addresses
Can we have say 10 users at a time connect to tenant 1 but send/receive as companyb.com. ie, we set the spf record and fwd their mail in tenant 2 to tenant 1. Maybe some trickery w/ adding their companyb.com as a non-internet upn, setting spfs and fwd their tenant mailboxes to our tenant.
Can't be the 1st person to do this, so looking for advice.