M

mail-based replication

A mechanism to replicate directory information through a messaging transport. This term applies to Exchange 5.x intersite directory replication as well as to Active Directory replication through SMTP.

mailbox recovery center

A feature of System Manager that lets you recover multiple disconnected mailboxes (i.e., mailboxes no longer associated with a user) simultaneously.

mail exchanger (MX) record

A record in a DNS database that indicates a host responsible for receiving e-mail messages.

MAPI

See Messaging Application Programming Interface (MAPI).

Masquerade Domain option

An option that allows you to indicate a different domain name to be placed in both the Mail From and From fields of all outgoing SMTP messages.

MCU

See multipoint control unit (MCU).

message tracking

A feature of an Exchange server that, along with the subject logging feature, provides a sophisticated way to track messages throughout the Exchange organization, primarily for troubleshooting purposes.

Message Transfer Agent (MTA)

The component in all versions of Exchange Server that transfers messages between servers, using the X.400 protocol.

Messaging Application Programming Interface (MAPI)

The application programming interface (API) used by Microsoft messaging applications such as Outlook to access collaboration data. MAPI, or more specifically, MAPI RPC, is also used as the transport protocol between Outlook clients and Exchange servers.

metabase

A store that contains metadata such as that used by IIS to obtain its configuration data. The metabase can be viewed through utilities such as Metaedit.

metabase update service

A component in Exchange that reads data from Active Directory and transposes it into the local IIS metabase. The metabase update service allows the administrator to make remote configuration changes to virtual servers without having a permanent connection to each system.

metadata

Data about data. In relation to Exchange, this term can be used in the context of Active Directory and can also be used to describe the structure within the store or the MTA.

MIME

See Multipurpose Internet Mail Extensions (MIME).

mount

To place an individual store in a storage group online. Stores can also be taken offline, or dismounted. You might dismount a store for maintenance, for example.

MTA

See Message Transfer Agent (MTA).

multipoint control unit (MCU)

A reference to the T.120 protocol, which allows clients to connect to data conferencing sessions. MCUs can communicate with each other to transfer conferencing information.

Multipurpose Internet Mail Extensions (MIME)

A standard that allows multiple files of various content types to be encapsulated into one message. RFCs 2045 through 2049 currently define MIME and are considered to be one single standard.

MX record

See mail exchanger (MX) record.