SMTP/POP3

the Server uses two protocols to move mail around. SMTP (Simple Mail Transfer Protocol) and POP3 (Post Office Protocol V3).

 

SMTP is a send protocol, used for sending mail from both the mail client to the Server and sending mail to the ISP (Internet Service Provider) mail server and on to the recipient.

 

POP3 is a retrieve protocol, used by the Server in the form of SmartPop to retrieve mail from a POP3 mailbox on the ISP’s server. Then there is the POP3 Service, which is the FTGate Server side implementation of the POP3 protocol. This provides POP3 mailboxes to store the user's mail, and also handles the access to the mailboxes.

 

So with that in mind, here is how mail is routed from the sender to the recipient:

 

 

The user (sender) creates the new message, enters the recipient’s address, subject and message text. The sender's mail client then uses the SMTP protocol to transmit the message to the Server.

 

The Server’s SMTP service receives the message and stores it to await onward transmission to the ISP’s server, again using the SMTP protocol. The message is then routed to the final recipient’s ISP using SMTP. The recipient would then retrieve the message using the POP3 protocol in either the mail client or their mail server.

 

Incoming mail can be delivered to the Server by the ISP using an SMTP feed (recipient 1 in the diagram) in which case some form of ‘Kick’ may be required to initiate the transfer (commonly ETRN or Finger). SMTP is also used to route mail direct to the Server  when using the Server with a permanent connection to the Internet.  This is achieved using the MX record from the DNS data for the domain.

 

Incoming mail can also be retrieved from your POP3 mailbox on the ISP’s server using SmartPop (recipient 2 in the diagram) in the Server (SmartPop uses POP3 to retrieve mail). The mail is then routed to the recipients’ mailbox folder to await the user’s mail client connection to retrieve the message; again this is achieved using the POP3 protocol.