Mail Transfer Agent

Mail Transfer Agent or (MTA) may also be referred to as message transfer agent or mail relay.  MTAs are software that essentially allows users to send email communications; this software transfers email messages from one computer to another using a client-server application architecture. In this client-server transfer, MTA will implement both the sending (client) and receiving (server) portions of the Simple Mail Transfer Protocol (SMTP).

Message transfer agents typically work through back end server applications, and users do not interact directly with this software. Instead, users will interact with a mail user agent. However, this process is fairly straightforward. A mail transfer agent receives mail from another MTA or a similar software such as a mail submission agent or mail user agent.  In this transfer, the SMTP will specify the transmission details. When an MTA receives an email messages, the software will add a “received” trace header to the message’s header. During this process, the message will build a sequential record of the MTAs that have handled the message.