Forum Discussion
Exchange Hybrid Deployment single forest multiple email domains
Peter, Thank you.
When I add any email domain in office 365 and verify this.> Obviously the domain will become Authoritative but it should not break mail flow to on-premise exchange , but it does.
after verifying all these email domains I will be running Azure AD Connect to Sync and convert them manged.
Abdul Farooque as long as all mail-enabled objects are synchronized to Azure, there should no problem with an authoritative domain. If the domain is set to authoritative, DBE (Directory Based Edge) blocking becomes active which means if a mail will be send to a non-existing recipient in EXO, it will be blocked.
During coexistence and your migration phase, change the domains to internal relay and then analyse the mail flow bevor changing it back to authoritative (and maybe consider switch the MX record to EOP as well).