SMTP vs. POP3 vs. IMAP

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Difference between SMTP, POP3 and IMAP

SMTP, POP3 and IMAP…the terms can be bewildering to most people, particularly to those with no knowledge of the inner workings of the email system that they regularly use. While you can in fact take full advantage of the many benefits of email without having to know the least bit about these mail delivery protocols, people who are planning to set up an email server would benefit from a bit of information regarding each, and that is precisely what this comparison article aims to provide.



SMTP or Simple Mail Transfer Protocol is used in the delivery of email from an email client to an email server. It is also used to deliver email from one server to another. The technology uses port 25. POP3 or Post Office Protocol is an email client that allows users to download email from email servers. A relatively simple protocol, POP3 has a relatively small feature set, and it doesn't really offer very much aside from download. POP3 works on the assumption that users download all the email from the server, before deleting them and disconnecting. POP3 uses port 110. IMAP or Internet Message Access Protocol is quite similar to POP3, in that it is also used to download email from a server. Aside from this function however, IMAP also allows users to keep their email on the server after accessing them. Because the protocol leaves the email on the server, IMAP has a lot more requirements with regard to disk space and CPU resources. IMAP uses port 143.

Advantages And Disadvantages 

The main drawback to SMTP is that it can be used only to send email and not to receive them. In addition, the use of SMTP is dependent on the system's network and/or ISP settings. The main advantage of POP3 on the other hand, is that the email can be stored on the server even after downloading it. This allows users to read their email at their own pace, even after cutting off Internet connection. The main drawback is that you may inadvertently delete spam email and even viruses in the process. The main advantage of IMAP is speed, since it requires only a relatively small amount of data to be passed.  Email messages will only be downloaded upon a specific request from the user. Other advantages include the ability to create email folders and/or mailboxes on the server itself, and user ability to delete messages.

In Use

SMTP is typically used by the Mail Transfer Agent or MTA for the delivery of email to the recipient's mail server. As mentioned previously, SMTP can only be used for sending emails. POP3 offers users a simple system for accessing mailboxes and downloading email messages. With POP3, the user has the option to download email from the server while retaining copies for later retrieval. IMAP requires the transfer of only a small amount of data, which means that it will work well even slow connections. In addition, IMAP offers a host of user access services as well.



  • Used in delivering email from one server to another
  • Cannot be used for receiving emails


  • Allows users to store email on the server even after downloading them
  • Is pretty basic compared to the other protocols


  • Requires only small amount of data to be transferred 
  • Will work even with slow Internet connections

Comparison of SMTP, POP3 and IMAP

Which one do you prefer?
  • SMTP
  • POP3
  • IMAP

Discuss It: comments 2

One clarification please. When deleting a message on one device and using IMAP, the message is deleted from the server (and hence gone from all devices), yes? If using POP3, deleting a message from one device leaves the message still accessable from the other devices, true?

  • Guest
  • Warren jones wrote on January 2015

What about smtpauth?

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