Configuring Exchange 2010 SMTP Connectors

Configuring Exchange 2010 SMTP Connectors
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The golden rule with Exchange 2010 SMTP connectors is don't do more than you have to. 

You probably need internet access, therefore by all means configure an SMTP connector to your ISP.  However, if you have multiple Exchange 2010 servers in the same site then they can communicate effectively without SMTP connectors.

Routing Strategies For Local Email

Emails addressed to recipients in the local Active Directory site are handled by the Hub Transport server.  It's the job of the categorizer to deliver the email to the correct mailbox server; whereupon the message is retrieved by a version of Outlook.

Routing Strategies For Remote Email

  1. Internal to Hub Transport --> Hub Transport different Active Directory site.
  2. Internal to Hub Transport server --> ISP Internet
  3. Internal to Hub Transport server --> Edge --> Internet

Receiving email uses the same routes as above, but in reverse.  Thus it follows that you can categorize messages into four groups: inbound or outbound, and local or remote.

Because every delivery strategy involves the Hub Transport server, you can appreciate why every Exchange 2010 organization needs at least one server with this role.  Indeed, Microsoft's recommendation is to have one server with the Hub Transport role in each Active Directory site.

Supporting Components for the Exchange 2010 SMTP Connectors

While the categorizer is at the heart of the message system, let us get to kn

ow the other important components, the Microsoft Exchange Mail Submission service, store driver and the submission queue.

  1. As soon as an Outlook users sends an email, the Microsoft Exchange Mail Submission service takes over.
  2. The Submission service then notifies a Hub Transport server in the local Active Directory site.
  3. The email is then sent to the for the categorizer's submission queue.
  4. The store driver uses MAPI to connects to a user's 'Outbox' folder, it then retrieves the message from the corresponding Mailbox server. 
  5. Then the store driver converts the MAPI format into the Summary-Transport Neutral Encapsulation Format (S/TNEF).  This format has no plain text part, and is in eight–bit binary format.
  6. Next, the store driver places the email into the submission queue and moves the message from the user's 'Outbox' to their 'Sent Items' folder.

Message Delivery

In addition to local delivery, email can also enter the submission queue from an SMTP Receive connector, or even from the Pickup directory.  The submission queue stores all messages safely on disk until the categorizer is ready to process them.

It is the categorizer that is responsible for calculating the best routing path, for converting content format, and applying any organizational message policies.  Incidentally, the categorizer on an Edge Transport server verifies the recipient's SMTP address of an inbound message before it places it in the delivery queue.

The incoming message is then routed to a Hub Transport server.  In a new development in Exchange 2010, the categoriz

er makes copies of messages that have multiple recipients. 

The categorizer processes each message in the submission queue in turn. If a message is intended for a Mailbox server in the same Active Directory site, the categorizer places the message in a local delivery queue.  The store driver then takes over and delivers the message to the Mailbox server role by using MAPI.

Guy Thomas is a computer consultant and writer with attitude and a great sense of humor.

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