Editing Mail Transport Agent

== Definition ==

[[Email]] is [[transmit]]ted across [[network]]s via '''Mail Transfer Agents''' ('''MTAs'''). MTAs [[communicate]] using the [[Simple Mail Transfer Protocol]] ([[SMTP]]) and act as both [[client]] and [[server]], depending on the situation. 

== Overview ==

For example, an MTA can act as a [[server]] when accepting an [[email message]] from an [[end user]]'s [[MUA]], then act as a [[client]] in [[connect]]ing to and transferring the [[message]] to the [[recipient]] [[domain]]'s MTA for final delivery.

MTAs can be described with more specialized language that denotes specific functions: 

* '''Mail Submission Agents (MSA):''' An MTA that accepts mail from [[MUA]]s and begins the [[transmission]] process by sending it to a MTA for further processing. Often the [[MSA]] and first-hop MTA is the same process, just fulfilling both roles.

* '''Mail Delivery Agent (MDA):''' An MTA that receives mail from an organization's inbound MTA and ultimately places the [[message]] in a specific [[mailbox]]. Like the [[MSA]], the [[MDA]] could be a combined in-bound MTA and [[MDA]] component.

MTAs may also perform various [[security]] functions to prevent [[malicious]] [[email]] from being delivered or include [[authentication]] [[credential]]s such as [[digital signature]]s. These [[security]] functions may be provided by other [[component]]s that act as lightweight MTAs or these functions may be added to MTAs via [[filter]]s or [[patch]]es.
[[Category:Definition]]
[[Category:E-mail]]
[[Category:Security]]