KB ID 0001297
On EE this morning someone asked this question and I realised I’ve never written it up. So If you want to add a new domain to an already working Exchange deployment how do you do it?
Firstly, you need to have purchased the new domain name, and have the DNS records setup properly for the new domain name. See the following article;
Add the New Domain Into Exchange 2016 / 2013
Log into Exchange Admin Center > Mail Flow > Accepted Domains > Add.
Add a sensible name > Enter the new domain name > Select Authoritative > Save.
Create a User Mailbox For the New Domain
If you only have a few users to setup you can do them manually within the Exchange Admin Center > Recipients > Mailboxes > Add.
On the properties of the new recipient you can edit the email addresses associated with it.
Change and add accordingly.
Remember for individual users to untick the ‘Automatically update email addresses based on the email address policy applied to this recipient’ > then change the Clients ‘Reply address’ > OK > Save.
Create an Email Address Policy And Apply It to an OU
The procedure above does not scale well if you have a lot of users to allocate a new domain to, so you can write a new email address policy, and apply it to a particular OU, then create/import your new users into this OU, mail enable them, and they will all get the correct Email addresses.
Mail flow > Email Address polices > Add.
Add a new policy with the email format you require;
Repeat to add multiple email address formats > Save.
Scroll down to where you want to apply the policy to and select ‘recipient container’, (because OU would have been to simple).
Select the OU with your users in > OK.
Note: You don’t have to use OU’s you can use other things like ‘department’ which will get read from the users AD object.
With the policy selected > Apply.
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