This video will show you how to set a domain or a subdomain between an organization that have to share the same SMTP address space between two or more different messaging systems. For example, you may have to share the SMTP address space between Exchange and a third-party messaging system, or between Exchange environments that are configured in different Active Directory forests. In these scenarios, users in each email system have the same domain suffix as part of their email addresses.
Learn who to set this up quickly with this video: https://technet.microsoft.com/en-us/library/bb124423(v=exchg.150).aspx
This video have been delivered by: Bruno RR Fernandes
See more on: https://aka.ms/o365supportcorner