Allnet ALL7008, User Manual

Page: 322 / 430

321
And the action of user to receive mail is as follows:
The PC that used by remote user will connect to his/her MTA directly, to
ask MTA to check if its mailbox has mails or not. After MTA check by MDA,
it will transfer the mail to the user’s MUA. Meanwhile, according to MUA
setting, MTA will choose to delete the Mailbox or to preserve it. (For the
next time when user receive the mail again, the preserved mail will be
downloaded again)
The protocol of send/receive e-mail is as follows:
1. Sending e-mail: It is a function of the process of sending the mail from MUA
to MTA, and transfer mail from MTA to the next MTA. At present, most of the
mail server uses SMTP Protocol (Simple Mail Transfer Protocol), and the
Port Number is 25.
2. Receiving e-mail: MUA connect to MTA user’s Mailbox by POP (Post Office
Protocol) in order to read or download the mail in user’s mailbox. At present,
common POP Protocol is POP3 (Post Office Protocol version 3), and the
Port Number is 110.
Generally, a MTA that provides sending/receiving mail function needs two
protocols at least. They are SMTP and POP3. And as long as your MUA and
MTA support SMPT and POP3, then they can connect with each other.
After MTA analyzing the received mail and if the recipient is not in the
master account, then MTA will transfer the mail to the next MTA. This function is
called Relay.