Adding additional SMTP email domains to Exchange 2007/2010 and SBS2008/SBS2011

Often companies operate more than one internet domain – sometimes they are simply “aliases” of each other (For example here at BlueCompute we use bluecompute.co.uk and bluecomp.co.uk interchangeably, and many companies who’ve changed their names over the years retain multiple domains) and sometimes they relate to different parts of the business – for example a company that buys and sells widgets may have the domains “webuywidgets.co.uk” and “wesellwidgets.co.uk” and use them for different websites and different users.

When you set up SBS you are required to enter an ”internet domain name” (or register a new one through Microsoft’s partners) as part of the “Set up your internet address” wizard. At this time you may only enter one domain name and this is used as the default for all users.

Exchange needs to know which domains it should accept email for and will reject emails that it receives for any other domains. The domains for which Exchange will accept emails are listed in the Exchange Management Console under Microsoft Exchange On-Premises –> Organization Configuration –> Hub Transport and are found in the “Accepted Domains” tab.

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Each entry has a descriptive name, a domain and a “Type” (discussed below).

Domain Types

The types of domain you can select are:

  • Authoritative Domain: This indicates that the Exchange server is the one and only email server responsible for addresses in this domain. If the server receives an email to a domain for which it is Authoritative and no local mailbox matches the address, the email will be returned to the sender undelivered.
  • Internal Relay Domain: This domain type is used if some of the email addresses for this domain live on the Exchange server, but some exist on another server, for example on Google Mail server. If the server receives an email to a domain which is configured as an Internal Relay domain and no local mailbox matches the address, Exchange will use a Send Connector to forward the email to additional servers.
  • External Relay Domain: This implies that none of the email addresses for this domain are hosted on the Exchange server, and any emails received to this domain will be forwarded through a send connector to some other server.

In the vast bulk of situations Authoritative Domain is the correct solution for domains that you use for Exchange email – the other types will require some thought and consideration, and may well be the subject of further posts.

Adding an Accepted Domain

On the “Accepted Domains” page, right-click in any empty space and select “New Accepted Domain…” In this example we’ll add the “wesellwidgets.co.uk” domain.

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Enter the descriptive name (usually much the same as the domain name itself, but if the domain name is not descriptive you might choose to use something like “Legacy domain for old users” or any other bit of text that’ll help you remember why it’s there next time you need to change something), enter the domain name that you wish to add and select the appropriate type.

Click “New”, and the domain will be created. You should see it listed in the “Accepted Domains” section. This domain will now be available to assign to users either directly or using an E-Mail Address Policy.

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