What are POP3 ,IMAP and SMTP?

SMTP, POP3 and IMAP are TCP/IP protocols used for mail delivery.If you've got a couple of minutes to spare, now's a good time to know what they are and how they differ from one another.


SMTP stands for Simple Mail Transfer Protocol, which is the protocol used to transport email messages from computer to another until they reach their destination.

SMTP is used between SMTP clients and SMTP mail servers, which deliver the email to its destination.

After that, SMTP is still used when SMTP mail servers forward the message to the next server, until it has been notified to the mail server for its final destination.


POP3 stands for Post Office Protocol version 3.

POP3 plays the main communication protocol or language which receives emails from an email server or service provider. POP3 is used by programs, for instance Thunderbird email, Microsoft Office Outlook, and other programs that use to communicate with other email servers. It can also be supported by an independent email program on other devices.

When POP3 is used, the email messages are moved to the computer where they are downloading - which means after successfully downloaded, they are deleted from the mail server on where they were stored.

Sometimes, POP3 is used to transfer email from a different email provider. For example, your Outlook.com email access to Gmail can be implemented by configuring Gmail to use POP3 to retrieve and transfer (fetch and transfer) Outlook.com email into your Gmail account.


IMAP stands for Internet Message Access Protocol.

The name implies that IMAP is a protocol to access e-mail. This is different from POP3, which is essentially a protocol to transfer (or move) message.

When IMAP is used by email programs for the purpose of accessing email messages stored on a server, the messages are retained on the server unless they are moved or totally deleted. The copies of email messages can be downloaded, but basically, IMAP delivers the best which can be called a window or an overview for emails stored on the server.

While the copy of the email can be downloaded and enables offline access, the IMAP protocol works best when continuously connecting to the email server. The changes on that server - like a new message arrives, an email is deleted or changed by a web interface or email program - soon to be notified in the program access to email server via IMAP.

Multiple-simultaneous access - means that more than one computer or device can access the same collection of emails at the same time - this is one of the IMAP’s strengths, and it is the technology usually used by mobile devices, and even the web interface, e-mail management that can be accessed from multiple locations. The downside is a more-or-less constant connection that's best used, as well as the fact that email on the mail server accumulates unless they are deleted, which sometimes is the reason to make the e-mail account to exceed the storage quota. (Exceed storage limit)


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