Mailing Servers

• For Sending and Receiving the mails is done by two Agents.
• Message Transfer Agent.
• Message Access Agent.
• Message Transfer Agents used to transfer message from client computer to the recipients mail server.(SMTP is the Message Transfer Agent).
• Message Access Agent used to send message from the recipient mail sever to recipient computer.(POP3 and IMAP are the Message Access Agent).

SMTP:

• SMTP stands for the Simple Mail Transfer Protocol.
• There are two MTAs, client MTA and server MTA.
• A client MTA at clients system sends mail which is received by the server MTA at client’s mail server.
• Client Mail Server has client MTA which sends the mail from client’s mail server to the server MTA at recipient’s mail server.
• By default, the SMTP protocol works on three ports:
  • Port 25 - this is the default SMTP non-encrypted port
  • Port 465 - this is the port used if you want to send messages using SMTP securely.

POP3:

• POP3 stands for the Post Office Protocol Version 3.
• POP3 has client and server MAA.
• Client MAA software is installed on the recipient computer.
• Server MAA is installed on the recipient’s mail server.
• To access/read the mail the user has to first download the mail from mailbox on mail server to its computer.
• Multiple client usage is not allowed in the POP3.
• POP3 can be used at one PC.
• POP3 protocol ports:
  • Port 110 - this is the default POP3 non-encrypted port
  • Port 995 - this is the port you need to use if you want to connect using POP3 securely

IMAP:

• IMAP stands for Internet Mail Accessing Protocol.
• Functionality of IMAP is same as POP3.
• It is more powerful, has more features and is more complex than POP3.
• Mails are stored in the Server, we can access them globally.
• It is useful for single account is accessed by multiple people.
• IMAP protocol ports:
• Port 143 - this is the default IMAP non-encrypted port.
• Port 993 - this is the port you need to use if you want to connect using IMAP securely.