MTA stacks refer to the non-SMTP message transfer service of Microsoft’s Exchange Server.  MTA stands for Message Transfer Agent and its stacks service is the one responsible for the implementation of Microsoft Exchange MTA communication. As a core component of the Exchange Server, the MTA stacks service relies heavily on the System Attendant which holds the data regarding DSAccess or Directory Service Access.  The data from this component is essential in terms of the retrieval by the MTA stacks service.  Through DSAccess, MTA Stacks will be able to get the necessary information regarding the recipient for message transfer and the corresponding configuration setup information.

The basic function of MTA Stacks is to provide a venue for the message transfer intended for external messaging environments or systems along with Exchange servers that are configured using X.400 connectors.  Through MTA Stacks, messages can be transported from an Exchange Server to various other points including other messaging software like Domino or Lotus Notes for example.  This is made possible by MTA Stacks through connectors that are classified as MAPI-based.  In terms of message transfer beyond the standard SMTP platform, MTA Stacks typically looks out for the delivery address or recipient.  Once this part of the process is defined, MTA stacks will then make sure that the message is copied and forwarded to an external inbox or forwarded to the next MTA available.

The function of MTA Stacks service is made efficient by means of communication with the other components in the message transfer outside of standard SMTP.  Aside from the Active Directory, MTA Stacks service also communicates and interacts with registry files to get the proper configuration settings and parameters. MTA Stacks also works hand in hand with the system’s routing manager in case some messages need to be redirected from its original recipient or destination.