What is SMTP, POP3 & IMAP & How does it Work ?

Last Updated 2 months ago

SMTP, POP3 & IMAP: Have you ever wondered about the technology behind the Emails sent by you everyday. It’s actually several simple technologies working together, technologies which we take for granted when we compose a message and click send. On the back of each email their is a powerful engine called the email server, this email server actually pushes the emails through the internet. All of us use them, but little did we know how does an email server work?

As you know To drive a car you need not have to be an expert to differentiate a carburettor from a tailpipe, but when your car breaks down, this little over the top knowledge helps. Email rarely crash but you should know how Pip’s mail reaches Estella across the globe in a moment. Here is the game play of SMTP, POP3 & IMAP.

Every email message is actually a text file plus the attachments. Just like other data through the internet, an email is also broken into smaller packets. As soon as you click the send button, all these packets are uploaded to a central computer (the email server) that hosts the email service.

This email service now comes into action and then start relaying these packets through the internet to that server which holds the email service of your recipient. Now The mail server of your recipient looks for its email address, then it locates it and places the email within the inbox. In fact this email client go around reassembling the packets into a complete mail. What happens next? Your recipient logs into her/his account and downloads the email. Job Done! See the magic of SMTP, POP3 & IMAP in action.

SMTP, POP3 & IMAP all three are actually TCP/IP protocols which are used for mail delivery. Just for your reference each protocol is actually a specific set of communication rules between various computers.


SMTP is an acronym of Simple Mail Transfer Protocol. The email server responsible for sending emails is called the SMTP. Going in details, SMTP is used when email is sent from an email client to an email server or when email is sent from one email server to another. SMTP make use of port 25.


POP3 is an acronym of Post Office Protocol. The function of POP3 is to allow an email client to download an email from an email server. However it should be noted that the POP3 protocol is basic and does not encases many features except of downloading. Its design makes an assumption that the email client downloads all available email from the server, deletes them from the server and then disconnects. POP3 generally uses port 110.


IMAP stands for Internet Message Access Protocol. IMAP is similar to POP3. It is also a protocol that an email client can use to download email from an email server. Bu the good news is that the IMAP includes many versatile features that POP3 lacks. The IMAP protocol is designed to let users keep their email on the server. However IMAP requires more CPU resources and more disk space on the server than POP3, as in this technology all emails are stored on the server. IMAP normally uses port 143.

So before sitting down to email next time; don’t forget to admire the synergy of technology that makes your emailing possible. An outreach platform for growth teams. Book 3X more sales meetings.


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