How to remove non-routable domains from your Exchange Organization

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Some organizations have non-routable domains wandering in the SMTP address of Exchange/Mailboxes. It is nice to keep the environment clean and remove non-used configuration, also if you are planning to have a hybrid environment, it is interesting to remove those invalid domains to some road-blocks down the road when integrating with Office365.


During the organization preparation which happens when the first Exchange Server is deployed, by default the FQDN of the Active Directory is going to be the first accepted domain of the organization and also be part of the e-mail address policies for that organization.

If your organization has a valid FQDN Active Directory domain o(something like or then you are good to go, however most of the companies use something like company.local, company.corp, and you get the idea, right?

For those companies that still have the non-routable domain around, we are going to perform a series of steps to remove that domain from your organization.

Email address policies..

The first step is to check it out if that non-routable domain is being applied to your users. Logged on the EAC, click on mail flow and then click on email address policies, in the new page click on email address format tab. If the domain is listed there, make sure to select it and remove from the list.

If there is more than an email address policies listed on that page, make sure that you go through each one of the policies before going to the next step.


Accepted domains..

Now that we know that our invalid domain is not being stamped on new users, we can go ahead and remove it from the Exchange Organization. Click on mail flow and then on accepted domains. All domains will be listed, if the invalid domain has the (default domain) as part of its name, then we need to select one of the existent domains to be the new default domain.


In the future primary domain, make sure that you select make this the default domain and then click on save.


Now that the invalid domain is not the default domain, we can remove it from our organization. Select the desired domain (in our case apatricio.local) and click on the Recycle Bin icon, and confirm the removal by hitting yes.


Email address at the mailbox level…

All changes that we performed so far are for the new mailboxes, so any new mailbox won’t have the invalid SMTP address stamped on their list of SMTP address.

However, an email address policy only adds information and it will never remove SMTP from the end users. That’s being said, all users created in the past will have an entry to the invalid SMTP address.

There are several ways to remove those SMTP address from the users, the simple way is to get properties of the user, and then delete the entry, as shown in the image below.


That works fine for a couple of users, but if you want to remove several users, then we can use ADModify or PowerShell. We will be showing both methods in a different Tutorial here at


In this Tutorial we went over the process of removing that non-routable domain from the Exchange Organization. This Tutorial is also recommended for organization that have that type of domain and want to create hybrid scenarios with Office365.

Written by Anderson Patricio

Anderson Patricio is a Canadian Exchange Server MVP and MCSM (Solutions Master) and he contributes to the Microsoft Community with articles, tutorials, blog posts, forums and book reviews. He is a regular contributor at, and (Portuguese).