The Role of the MTA
The Role of the MTA
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The role of the message transfer agent (MTA) in message transfer has been significantly reduced in Microsoft® Exchange 2000 Server. Earlier versions of Exchange were built around the X.400-connector based MTA, which routed messages between servers within a site, to MTAs at other sites, and to and from foreign (non-Exchange) networks. With Exchange 2000 Server, Microsoft has moved to institute SMTP as its native transport mechanism. This is due to the increased sophistication and widespread use of SMTP. The MTA is still in use, but it is no longer responsible for routing messages. Instead, it is a repository for messages sent to and from foreign systems and Exchange Server 5.5 servers.
The following table summarizes the roles of the MTA in Exchange Server 5.5 and Exchange 2000 Server:
| Exchange 5.5 | Exchange 2000 |
|---|---|
| Controls intra-Exchange site remote procedure call (RPC) messaging. | Sites replaced by Routing Groups. SMTP is used to send messages between Routing Group members. |
| Controls traffic between site connectors and X.400 connectors. | Can connect old Exchange sites to Exchange 2000 Server organizations, but SMTP is used in most situations. |
| Determines message routing through the Gateway Address Routing Table (GWART). | Routing is dynamically determined by the MS Exchange Routing Engine, using a link state algorithm to determine the best message route. |
| Manages connections for X.400 messaging systems. | No change. |
| Manages EDK-based connectors and gateways. Most FAX connectors are in this category. | No change. |
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