A mail transfer agent (MTA) (also called a mail transport agent, message transfer agent, or smtpd (short for SMTP daemon)), is a computer program or software agent that transfers electronic mail messages from one computer to another. Simple Mail Transfer Protocol ( SMTP) is a De facto standard for electronic mail (e-mail transmissions across the Internet. In Unix and other computer multitasking Operating systems a daemon (ˈdiːmən or /ˈdeɪmən/ is a Computer program that runs in the background Computer programs (also software programs, or just programs) are instructions for a Computer. In Computer science, a software agent is a piece of software that acts for a user or other program in a relationship of agency. Electronic mail, often abbreviated to e-mail, email, or originally eMail, is a Store-and-forward method of writing sending receiving

The term mail server is also used to mean a computer acting as an MTA that is running the appropriate software. A computer is a Machine that manipulates data according to a list of instructions. The term mail exchanger (MX), in the context of the Domain Name System formally refers to an IP address assigned to a device hosting a mail server, and by extension also indicates the server itself. The Domain Name System (DNS is a hierarchical naming system for computers services or any resource participating in the Internet. An Internet Protocol ( IP) address is a numerical identification ( Logical address) that is assigned to devices participating in a Computer network

Overview

An MTA receives mail from another MTA (relaying), from a mail user agent (MUA), thus acting as a mail submission agent (MSA), or from an MSA that got the mail from an MUA. An e-mail client, aka Mail User Agent (MUA aka e-mail reader is a frontend Computer program used to manage E-mail. A mail submission agent or The MTA works behind the scenes, while the user usually interacts with the MUA. Every time an MTA receives an e-mail, it will add a "Received:" trace header field to the top of the message. In this way, there is a record of which MTAs handled the e-mail and in which order. Upon final delivery, the "Return-Path:" header will also be added to record the return path. A bounce address is an E-mail address where Bounce messages are delivered to

The delivery of e-mail to a user's mailbox typically takes place via a mail delivery agent (MDA); many MTAs have basic MDA functionality built in, but a dedicated MDA like procmail can provide more sophistication. A Mail Delivery Agent ( MDA) is Software that delivers E-mail messages right after they've been accepted on a server distributing them to recipients' individual Procmail is a Mail delivery agent (MDA or Mail filter, a program to process incoming Emails on a computer widely used on Unix systems

According to one survey, sendmail, Microsoft Exchange Server, Postfix, and Exim together control over 85% of market share for SMTP service. Sendmail is a Mail transfer agent (MTA that supports many kinds of mail transfer and delivery including the overwhelmingly popular SMTP. Microsoft Exchange Server is a Messaging and Collaborative software product developed by Microsoft. Postfix is a free open source Mail transfer agent (MTA a Computer program for the routing and delivery of Email. Exim is a Mail transfer agent (MTA used on Unix-like operating systems ^[1] Another survey suggests a more balanced playing field, though it included hosted email services such as Postini. Postini is an Email and Web security company founded in 1999 and originally based in San Carlos California, United States. ^[2]

See also

• MX record
• List of mail servers
• Comparison of mail servers
• Mail user agent
• Mail delivery agent

References

---

© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic