Forum Discussion
Adding a new domain (company acquisition) to existing Office 365 Environment
Hi, Our company ( hybrid, 600 E3 users) acquired a company ( calling it X 200 user exchange 2010) my question is when is the right time to add the domain name X.com to our office 365 environment. ...
Hi!
Vasil is right. Unless you add a send connector and set the domain to internal relay then if the existing users on 365 send mail to that domain it’s going to look internally within Office 365 and bounce.
So,
1./ Add domain, txt and validate and add the Exchange service, do not change any other DNS records
The domain goes onto Exchange Online at this point. If you don’t do steps 2 and 3 you may start experiencing bounce backs if users send mail from the existing users to the newly added domain. This is expected behaviour.
2./ Go into Exchange Admin Console and in Accepted Domains change the newly added domain to internal relay domain
3./ In The Exchange Admin Console Add a outbound connector (from Office 365 to the existing mail platform) for the newly added domain pointing to the highest priority MX record on that domain.
https://docs.microsoft.com/en-us/exchange/mail-flow-best-practices/use-connectors-to-configure-mail-flow/set-up-connectors-to-route-mail
That should work and ensure mail flows back to the new domain’s mail platform from Office 365 users.
You may want to do this change out of hours or notify the existing 365 users so they do not send mail between the domains at the time you make these changes.
Hope that helps
Best, Chris
Vasil is right. Unless you add a send connector and set the domain to internal relay then if the existing users on 365 send mail to that domain it’s going to look internally within Office 365 and bounce.
So,
1./ Add domain, txt and validate and add the Exchange service, do not change any other DNS records
The domain goes onto Exchange Online at this point. If you don’t do steps 2 and 3 you may start experiencing bounce backs if users send mail from the existing users to the newly added domain. This is expected behaviour.
2./ Go into Exchange Admin Console and in Accepted Domains change the newly added domain to internal relay domain
3./ In The Exchange Admin Console Add a outbound connector (from Office 365 to the existing mail platform) for the newly added domain pointing to the highest priority MX record on that domain.
https://docs.microsoft.com/en-us/exchange/mail-flow-best-practices/use-connectors-to-configure-mail-flow/set-up-connectors-to-route-mail
That should work and ensure mail flows back to the new domain’s mail platform from Office 365 users.
You may want to do this change out of hours or notify the existing 365 users so they do not send mail between the domains at the time you make these changes.
Hope that helps
Best, Chris
Hi Chris, I really appreciate your reply, in step 1 should I enable the Exchange services to proceed or I can leave it no configured.I am confused because we haven`t migrated any mailboxes from their end and haven`t decided if we going to do a cut-over or hybrid migration yet.
Thanks
Aysan
- Yes, you should enable Exchange services to proceed otherwise the domain will never go onto Exchange Online and you will not be able to do steps 2 and 3.
If you are unsure about the migration route to take, I would advise not to proceed with adding the domain until you have a clear migration methodology. As Vasil said, it is only 200 users so this usually fits a cutover migration. You can check out the ways to migrate to Office 365 here
https://docs.microsoft.com/en-us/exchange/mailbox-migration/office-365-migration-best-practices
https://docs.microsoft.com/en-us/exchange/mailbox-migration/mailbox-migration
And follow this guidance.
Best, ChrisThank you, as on our company we are using hybrid exchange, which method of migration make sense?
is there any easy way to give the users access to ourdomain email address, before setting up a trust between 2 Ad`s first?
Thank you so much!
Aysan
- Hi Aysani
Without doing a discovery, it is difficult to say because as you know there are many factors involved in a migration such as number of sites, business objectives, third party applications etc. However, by definition and taking into account that the Exchange 2010 server is out of support soon, then the easiest is a cutover migration where all those users move at once and then decommission of the Exchange Server, The users would be cloud users on Office 365. In this scenario you can have either domain as the primary SMTP and the other as the alias.
Whether you consolidate their AD after, so you bring them into your Hybrid Setup - I think that depends where you want to get to and how best you think to manage your users. Personally, with things moving more into the Cloud I would personally cutover onto 365 and then manage them through Azure AD with a view to coming out of Hybrid and doing all the management in Azure AD for the whole organisation. However, that's a personal opinion where others may prefer remaining in hybrid.
Best, Chris
- Yeah, for some readon I had a tenant to tenant migration in mind! In this cAse Chris Hoard is right and ms tools will suffice! Just to not any confusion
Adam
