How emails work?
. E-mail is the exchange of messages through internet.
. It uses different protocols to send and receive messages from its server:
SMTP
POP
IMAP
What is SMTP?
. To send and receive mails, we need Mail Transfer Agent and Mail Access Agent.
. Simple Mail Transfer Protocol is a Mail Transfer Agent (MTA).
. There are two MTAs: Client MTA and Server MTA.
. Client MTA at client's system sends mail to the Server MTA at client mail server.
. Now Client MTA at client's mail server forwards this mail to the Server MTA of receiver's mail server.
. Sender and receiver must be connected to their mail server through WAN or LAN.
. SMTP is used in two steps - In between sender and its mail server and in between client's mail server and receiver's mail server.
What is POP?
. Post Office Protocol is a Mail Access Agent (MAA).
. POP3 is a 3rd version of POP.
. It is used to pull the mail from server MTA and handle it to receiver.
. There are two MAAs: Client MAA and Server MAA.
. Client MAA is installed in the receiver's computer and Server MAA is present in the Mail server.
. To read or access mail from server, Client MAA establishes connection with server MAA.
. When user logs in, Client MAA at receiver sends username and password to the mail server.
. Using POP, whenever we access a mail, it gets downloaded in the local computer where we opened and it gets disappeared in the mailserver.
. We couldn't open that mail in other devices which is a major disadvantage.
. So we use Internet Mail Access Protocol (IMAP) which stores mails in the mailbox and we can open them in any devices.
SMTP Vs POP3:
| SMTP | POP3 |
|---|---|
| Simple Mail Transfer Protocol | Post Office Protocol version3 |
| Mail Transfer Agent | Mail Access Agent |
| Applied between sender and sender's mail server and sender's mail server to receiver's mail server | Applied between receiver and receiver's mail server |
| Allows to send mail from sender to mail box in receiver's mail server | Allows to retreive mail from receiver's mail server to receiver's computer |
| Uses port 25 in TCP for transmission | Uses port 110 in TCP for transmisson |