Exchange Server 2007 contains a completely new implementation of email routing. Each of the Active Directory service sites where Exchange mailboxes are hosted must have a Hub Transport server role to control messaging between sites, even within a single site.The exchange 2007 use Active directory site links to route the e-mails.
Diagram for Mailflow
Message transport components:
- Receive connectors
- Send Connectors
- Submission Queue
- Delivery queue
- Store driver
- Exchange Mail submission service
- Pickup directory
1) SMTP Receive connector:
- Used to receive the e-mail from internet.
- Configured at edge or hub transport server
- No need to configure receive connector in same forest to route the e-mails between hub servers.
2) SMTP Send connector:
- Used to send the e-mail to any smtp server.
- It may be to internet or any smtp server with in the organization.
3) Submission Queue:
- The transport server role[Hub or edge transport server] has the submission queue.
- Submission queue has created by categorizer when Exchange Transport Service starts. It stores all messages on the local hard disk until they are processed by the categorizer for delivery.
The categorizer always picks the oldest message from the Submission queue and checks whether this message has tThe store driver on the Hub Transport retrieves it from the user’s Outbox and then transfers it to the submission queue.o be routed internally in the Exchange organization or externally.
On each Hub Transport server the categorizer performs the following tasks:
- Identification and verification of recipients
- Expansion of distribution lists
- Determination of routing paths
- Conversion of content formats
- Application of message policies
5) Delivery queue
- A queue that is used to hold messages that being delivered to a Mailbox server or remote location. A delivery queue is created for each unique message destination.
- The store driver on the Hub Transport retrieves it from the user’s Outbox and then transfers it to the submission queue.
- After submitted to the submission queue, the e-mail moved to sent items from outbox.
- The submission queue also taking care of the messages that are stored in MAPI format has been converted to Summary Transport Neutral Encapsulation Format (S/TNEF) before being placed in the Submission Queue
7) Exchange Mail submission service
- This service runs on the mailbox server role.
- It notifies the Hub Transport server role to pick up the message from the sender’s Outbox.
- If there are multiple Hub Transport server roles on one Active Directory site, the Message Exchange Mail Submission service attempts to evenly distribute notifications between each transport role using static load balancing.
- Each message that is transferred to the pickup directory has been successfully submitted to the submission queue via the categorizer.
- Messages placed in the Pickup Directory must be in the appropriate format and have read/write permissions configured.
- It allows you to take a properly formatted text file and have the Hub Transport server role process and deliver it.
- 3rd party applications may place messages in the Pickup directory rather than communicating directly with the Exchange Server.
- By default, the pickup folder is found in the \Program Files\Microsoft\Exchange Server\TransportRolesfolder on the drive that you installed Exchange