Using two shared email systems within the same domain in Exchange 2013

A shared namespace occurs when an organization uses more than one email systems for the domain. For example - say Company A ([email protected]) merges with Company B ([email protected]) and forms Company C ([email protected]) and Company A uses a linux MDA (Mail Delivery Agent) e.g. Dovecot and Company B uses

Exchange to provide email access to users - you will be faced with a situation where half of the users of the new domain (companyc.com) will be using Dovecot and the other half using Exchange.


So in order to allow this scenerio to function we will firstly change the accepted domain type of domainc.com to an "Internal Relay." And then create a new "Send Connector" to instruct Exchange where to send all of the emails

Set-AcceptedDomain companyc.com -DomainType InternalRelay

Below describes the function of the three domain types available in Exchange (taken from TechNet):

Authoritative Domain: Select this option if this domain is used for e-mail addresses of the recipients in your organization.

Internal Relay Domain: To specify that e-mail messages are either delivered to recipients in your organization or relayed to a server outside your Exchange organization but still under the authority of your company or IT department, select this option.

External Relay Domain: To specify that e-mail messages sent to recipients in this domain are relayed to an e-mail server outside your organization, select this option.that do not have local recipients in AD.





Now we simply need to specify where the destined mail for the non-AD recipients goes:

New-SendConnector -Name "Internal Relay" -Custom -AddressSpaces companyc.com -SmartHosts 192.168.1.200 -SourceTransportServers ex2007.mycompany.local