AirLive RS-3000 - Manual (Page 163)

The flow of delivering e-mail:
The three key element of sending e-mail are: MUA, MTA, MDA
 MUA (Mail User Agent): The PC of client cannot send mail directly. It must deliver mail by MUA.
No matter to send or to receive the mail, the Client user still has to use mail system by MUA that
provided by operation system. For example: Outlook Express in Windows is MUA. The main
function of MUA is to receive or send e-mail from mail master and provide the function for users to
browse and edit mail
 MTA (Mail Transfer Agent): When the user sending or receiving mails, they are both completed
by MTA. Basically, its functions are as below:
1. To receive the mail that sent by external master: when receiving the mails from external; only if the
recipient exists in MTA internal account then this mail will be received by MTA.
2. To send mail for user: Only if the user has the authority to use MTA, and then the mail can be sent
by MTA.
3. To let user to receive his/her own mail: The user can take the mails to his/her own PC from mail
master.
Generally the Mail Server we refer to is talking about MTA.
 MDA (Mail Delivery Agent): To let the mail that received by MTA be put in the Mailbox according
to its destination. Or by MTA to send the mail to the next MTA.
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