GAPTHEGURU

Geek with special skills

Understanding Exchange Server Accepted Domain

Exchange  Server 2007 introduced new terminology for describing the
domain names  that it will accept email for, and what it will do with
that email.   This is referred to in Exchange Server 2007 as Accepted
Domains.

In Microsoft’s own words, “an accepted domain is any Simple Mail
Transfer Protocol (SMTP) namespace for which a Microsoft Exchange
organization sends or receives e-mail.”

Accepted Domains fall into one of 3 categories – Authoritative, Internal Relay, and External Relay.  Any given namespace that is an Accepted Domain can be only one of those three types.

Authoritative Domains

Authoritative Domains are those for which an Exchange organization
hosts mailboxes that have email addresses that use that domain.

For example, a company named Contoso Pty Ltd may own the domain name contoso.com and use email addresses of name@contoso.com.  The Exchange organization would be configured to consider contoso.com an Authoritative Domain.

An organization can have more than one Authoritative Domain
configured.  Using Contoso Pty Ltd as an example again, they may have a
second brand name of Contoso Services and use the contososervices.com
domain name in marketing materials.  In this case the Exchange
organization would be configured with both contoso.com and
contososervices.com as Authoritative Domains.

Internal Relay Domains

Internal Relay domains are those for which an Exchange organization
hosts some, but not all of the mailboxes that use that domain.  This
scenario is sometimes also referred to as a “shared SMTP namespace”.

Internal Relay domains are common when two companies have merged but
are yet to consolidate their Exchange environment into a single
organization.  When they have a need for consistent email addressing
across both Exchange environments Internal Relay domains are the
solution.

When an Accepted Domain is configured as Internal Relay it tells the
Exchange organization to accept mail for that domain, but if no
recipient in that organization has that email address then it looks to
the list of Send Connectors to determine where to send it next.

For example, if Contoso Pty Ltd and Northwind Traders formed a new company Contoso Traders with a new domain name of contosotraders.com, then each existing Exchange organization is configured with two items to share the SMTP namespace:

    • An Internal Relay domain of contosotraders.com
    • A Send Connector for the namespace contosotraders.com that sends email for unknown recipients to the other Exchange organization

External Relay Domains

External Relay domains are those for which an Exchange organization
will accept email, but hosts no mailboxes for that domain.  This
scenario might occur when one organization is acting as an ISP for other
organizations, or offering services such as email content filtering.

External Relay domains are used when one Exchange organization is
accepting email from the internet for a non-authoritative domain name,
and then forwarding it on to the authoritative Exchange organization.
This is usually performed at the Edge Transport Server to keep email for
non-authoritative domains from entering the corporate network.  For
this to occur the Edge Transport Server is configured with two items:

    • An External Relay domain
    • A Send Connector for the namespace that sends the emails to the authoritative Exchange organization

In these scenarios it is also common for the Edge Transport Server to
be used as an outbound email relay, or smart host, for the
authoritative Exchange organization.

Summary

For most Exchange organizations the Authoritative Domain type is the
only one used, however it is important for email administrators to
understand the full capabilities of Accepted Domains as explained above

4 Comments »

  1. Thank you.
    “Accepted Domains fall into one of 3 categories – Authoritative, Internal Relay, and External Relay” , that was the line that made me understand the difference.
    I thought accepted domains was a part of Authoritative domains.

    Comment by Dudex | 06/23/2012 | Reply

    • your welcome. I am happy my post helped you.

      Regards

      Comment by gaptheguru | 07/10/2012 | Reply

  2. This really help me understand the differences, thank you!

    Comment by Ron Steurer | 02/19/2013 | Reply

  3. Realy a great post

    Comment by Dinesh Rajpurohit | 07/03/2013 | Reply


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