The X. It is the network protocol that operates on top of HDLC so that the local system can communicate with the next node in the X. The values of these measures reveal the effectiveness of the X. Privacy Policy Terms of Use. Account Settings Logout. All Files. Submit Search. You are here:. Configurable parameters for the test Parameters Description Test Period How often should the test be executed.
Port The port number through which the Exchange server communicates. IsPassive If the value chosen is Yes , then the Exchange server under consideration is a passive server in an Exchange cluster. Free elements Indicates the number of free buffer elements currently in the MTA pool. Number This number can be used to determine whether additional processors might be beneficial.
Work queue length in MTA Indicates the number of outstanding messages currently in the work queue. Number This value represents the number of messages not yet processed to completion by the MTA. X25 transmit rate The rate at which data is transmitted over an X.
All rights reserved. Filter: All Files Submit Search. Test Period. How often should the test be executed. MTAs also form a core component of any X. These data files are related to problems with connectors that involve unprocessed messages. If mtacheck finds any problems, it tries to fix them. In a typical scenario, when an object in the MTA is damaged and blocks the messaging queue, mtacheck finds the object and removes it, placing it in a file so that you can examine it later.
You should run the Mtacheck command at least twice until you see the message: Database clean, no errors detected. In Exchange or later, a delivery group might span multiple Active Directory sites, and there might be multiple least-cost routing paths to those sites. Exchange designates a single Active Directory site in the destination delivery group as the primary site.
The primary site is closest Active Directory site based on the routing logic described earlier. To successfully route messages between delivery groups, Exchange takes the following issues into consideration:. The presence of one or more hub sites along the least-cost routing path : If the least-cost routing path to the primary site contains any hub sites, the message must be routed through the hub sites.
The closest hub site along the least-cost routing path is selected as a new delivery group of the type AD site , which includes all transport servers in the hub site. After the message traverses the hub site, routing of the message along the least-cost routing path continues.
If the primary site happens to be a hub site, the primary site is still considered a hub site for the following reasons:. If the destination delivery group spans multiple Active Directory sites, the source server should only attempt to connect to the servers in the hub site. As in previous version of Exchange, hub sites that aren't in the least-cost routing path to the primary site are ignored.
The target Exchange server to select in the destination routing group : When the destination delivery group spans multiple Active Directory sites, the routing path to specific servers within the delivery group might have different costs.
Servers located in the closest Active Directory site are selected as the target servers for the delivery group based on the least-cost routing path, and the Active Directory site those servers are in is selected as the primary site. Fallback options when connection attempts to all servers in the destination routing group fail : If the destination delivery group spans multiple Active Directory sites, the first fallback option is all other servers in the destination delivery group in other Active Directory sites that aren't selected as target servers.
Server selection is based on the least-cost routing path to the other Active Directory sites. If the destination delivery group has any servers in the local Active Directory site, there are no other fallback options because the message is already as close to the target routing destination as possible.
If the destination delivery group has servers in remote Active Directory sites, the option is to try to connect to all other servers in the primary site. If that fails, a backoff path in the least-cost routing path to the primary site is used. Exchange tries to deliver the message as close to the destination as possible by backing off, hop by hop, along the least-cost routing path until a connection is made.
The way that Exchange routes messages between Active Directory sites is virtually the same as Exchange For outgoing messages, the Transport service communicates with the Front End Transport service only when it's specifically configured to do so.
For more information, see Configure Send connectors to proxy outbound mail. For incoming messages, the Front End Transport service must quickly find a single, healthy Transport service to receive the message transmission, regardless of the number or type of recipients. Failure to do so results in the email service being perceived as unavailable by the sending server.
Like the Transport service, the Front End Transport service loads routing tables based on information from Active Directory, and uses delivery groups to determine how to route messages. However, the routing tables used by the Front End Transport service have the following unique characteristics:.
The Front End Transport service is never considered a member of a delivery group, even when the Mailbox server and the Client access server are installed on the same physical server which is always the case in Exchange or later. This forces the Front End Transport service to communicate only with the Transport service. The routing tables contain a special list of Mailbox servers in the local Active Directory site for fast fail-over purposes. Routing in the Front End Transport service resolves message recipients to mailbox databases.
The list of Mailbox servers used by the Front End Transport service is based on the mailbox databases of the message recipients. Note that it's possible that none of the recipients have mailboxes, for example, if the recipient is a distribution group or a mail user. For each mailbox database, the Front End Transport service looks up the delivery group and the associated routing information.
The delivery groups used by the Front End Transport service are:. Depending on the number and type of recipients, the Front End Transport service performs one of the following actions:. For messages with a single mailbox recipient, select a Mailbox server in the target delivery group, and give preference to the Mailbox server based on the proximity of the Active Directory site. Routing the message to the recipient might involve routing the message through a hub site.
For messages with multiple mailbox recipients, use the first 20 recipients to select a Mailbox server in the closest delivery group, based on the proximity of the Active Directory site. Note that message bifurcation doesn't occur in Front End Transport, so only one Mailbox server is ultimately selected, regardless of number of recipients in a message. If the message has no mailbox recipients, select a random Mailbox server in the local Active Directory site.
The Mailbox Transport service is stateless, and doesn't use message delivery queues. Like the Transport service, the Mailbox Transport service loads routing tables based on information from Active Directory, and uses delivery groups to determine how to route messages.
However, there are routing aspects that are unique to the Mailbox Transport service:. Because the Transport service and the Mailbox Transport service exist on the same Mailbox server, the Mailbox Transport service always belongs to the same delivery group as the Mailbox server. This delivery group is referred to as the local delivery group. The Mailbox Transport Submission service doesn't automatically send messages to the Transport service on the local Mailbox server or on other Mailbox servers in its own local delivery group.
The Mailbox Transport Submission service has access to the same routing topology information as the Transport service, so the Mailbox Transport submission service can send messages to the Transport service on Mailbox servers outside the delivery group. The Mailbox servers in the local delivery group are used as fallback options, and for delivery to non-mailbox recipients.
The Mailbox Transport service only communicates with local mailbox databases. The Mailbox Transport service never communicates with mailbox databases on other Mailbox servers. When a user sends a message from their mailbox, the Mailbox Transport Submission service resolves the message recipients to mailbox databases.
The list of Mailbox servers used by the Mailbox Transport Submission service is based on the mailbox databases of the message recipients. For each mailbox database, the Mailbox Transport Submission service looks up the delivery group and the associated routing information.
The delivery groups used by the Mailbox Transport Submission service are:. Depending on the number and type of recipients, the Mailbox Transport Submission service performs one of the following actions:. When the Mailbox Transport Delivery service receives a message from the Transport service, it accepts or rejects the message for delivery to a local mailbox database.
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