Enable email flow for subdomains in EOP


Topic Last Modified: 2014-04-28

If the accepted domains that you’re using with Exchange Online Protection (EOP) have subdomains, you can enable email flow to and from these subdomains. For example, if you have an accepted domain called Contoso.com, and you enable match subdomains, users can send email to and receive email from all subdomains of Contoso.com, such as marketing.contoso.com and nwregion.contoso.com. In order to enable match subdomains, you must set up the accepted domain as an internal relay. For information about setting the domain type, see Manage Accepted Domains in EOP.

In Microsoft Forefront Online Protection for Exchange (FOPE), this feature was called catch-all domains.
If you have a limited number of subdomains, and you know all the subdomain names, we recommend setting up each subdomain as an accepted domain by using the Office 365 admin center, rather than using the procedures in this topic. By setting up each subdomain separately, you can have finer control over mail flow and include unique transport rules for each subdomain. For more information about adding a domain in the Office 365 admin center, see Add your domain to Office 365.

  • Estimated time to complete: 5 minutes

  • You need to be assigned permissions before you can perform this procedure or procedures. To see what permissions you need, see the "Domains" entry in the Feature permissions in EOP topic.

  • For information about keyboard shortcuts that may apply to the procedures in this topic, see Keyboard shortcuts in the Exchange admin center.

Having problems? Ask for help in the Exchange forums. Visit the forums at: Exchange Server, Exchange Online, or Exchange Online Protection.

  1. In the EAC, go to Mail Flow > Accepted domains, and select the domain.

  2. Verify that Internal Relay is selected.

  3. Select Match subdomains for this domain for sending and receiving emails.

To add match subdomains to a domain that is set up as an internal relay, use the following syntax:

Set-AcceptedDomain -Identity <Domain Name> -MatchSubdomains $true 

The following example sets up match subdomains for the contoso.com domain:

Set-AcceptedDomain -Identity contoso.com -MatchSubdomains $true 

For more information about using the Shell, see Set-AcceptedDomain and PowerShell in Exchange Online Protection.

To verify that you successfully added match subdomains to a domain, do the following:

  1. Run the command Get-RemoteDomain <Domain Name> | Format-List to verify the MatchSubdomains setting.