compare Email Protocols: IMAP, POP3, SMTP and HTTP

what is the difference of Email Protocols: IMAP, POP3, SMTP and HTTP. any body can explain what is the difference.
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John-Charles-HerzbergConnect With a Mentor Commented:

POP (Post Office Protocol)

Most of us use an email protocol called POP. It is currently the widest used form of email management. POP (or POP3) is the protocol, or “language”, that’s used to download your email from your ISP to your mail program. But why “POP”? or 3?

“POP” is pretty simple; it’s an acronym for “Post Office Protocol”. A communications “protocol” is just the language used between your email program and your ISP’s mail server. POP3 is simply the current revision of the POP protocol just like OS X 10.3, 10.4, 10.5 etc…

To configure a POP account you need three pieces of information:

The name of your ISP’s mail server that holds your email. Typically it’s something like “” or “”.
The name of the account you were assigned by your ISP. This may or may not be your email name, or something like it, or something completely unrelated. Check with your ISP for details.
The password to your account.
That’s it. With that properly configured, you can download email from your ISP directly to your computer.

IMAP (Internet Message Access Protocol)

The whole point of IMAP is that your email is stored on a remote server. It is especially useful to computer users who use more than one machine. I use IMAP extensively as I regularly use a desktop and a laptop. With IMAP, if I send or receive from one machine, the next time I launch Mail on the other machine, my mailboxes are synched with the remote server so as to be identical on both machines.

IMAP also supports several modes of operation. In “offline” mode, IMAP enables the user to continue working on new draft messages and stored copies of old incoming mail, and then synchronizes everything as necessary when a network connection is available again.

IMAP brings extra features that go way beyond what POP offers. It allows the client access to multiple folders, and indeed the right to manipulate folders directly on the server. There’s also the option to share folders with other users; with this in place, people can collaborate on work without the need to endlessly copy or forward messages among one another. IMAP offers users the chance to create their own flexible folder hierarchy. It’s a far more powerful protocol than POP, although that makes it somewhat more complicated to use.

You configure an IMAP account with the same basic information you use for a POP account.
Scott Fell, EE MVEConnect With a Mentor Developer & EE ModeratorCommented:
John-Charles-HerzbergP gave you a nice description.  POP and IMAP are for receiving email.  SMTP is the protocol that is used for sending your email.  HTTP is not really a protocol for email as far as I know.  I think when you see HTTP email that is referring to a web mail system like gmail and many corporate email systems have a webmail system as well.

I will add  POP and IMAP refer to the choices you will add to your email client (desktop email software) such as outlook or Mac Mail and sometimes web mail allows you to read outside email accounts via POP or IMAP.

Typically, when you choose POP for receiving your email a message is sent to the email server that the email has been accessed and that message will not be downloaded again by that email client.  This also means it is not the best thing to use when you are trying to access your email from multiple devices.  You can set your email client to "not remove from server" for X amount of days.  But that is still not very reliable when you have multiple devices.

For multiple devices, IMAP is the  way to go.  When you are using IMAP with your email client, you have the option to view the folders on the server in addition to your inbox.  So if you move an email in one device to a subfolder that is connected to the email server, you will see it in the other device.  

Another advantage to IMAP is a service called IDLE.  If your email server has this turned on, then using IMAP with IDLE is almost like using PUSH email.  The downside to this is it keeps a constant connection open to the email server.  For this reason, some inexpensive hosting accounts will not support this because it takes up a lot of resources.  I found if you use gmail or even the free gmail apps for business IDLE is available and email gets to my phone and desktop very quickly.
Manpreet SIngh KhatraConnect With a Mentor Solutions Architect, Project LeadCommented:
POP3 (Post Office Protocol 3) (PORT 110)  - It is the most recent version of a standard protocol for receiving e-mail. POP3 is a client/server protocol in which e-mail is received and held for you by your Internet server. Periodically, you (or your client e-mail receiver) check your mail-box on the server and download any mail, probably using POP3. This standard protocol is built into most popular e-mail products, such as Eudora and Outlook Express. It's also built into the Netscape and Microsoft Internet Explorer browsers.

POP3 is designed to delete mail on the server as soon as the user has downloaded it. However, some implementations allow users or an administrator to specify that mail be saved for some period of time. POP can be thought of as a "store-and-forward" service.

An alternative protocol is Internet Message Access Protocol (IMAP). IMAP provides the user more capabilities for retaining e-mail on the server and for organizing it in folders on the server. IMAP can be thought of as a remote file server.

POP and IMAP deal with the receiving of e-mail and are not to be confused with the Simple Mail Transfer Protocol (SMTP), a protocol for transferring e-mail across the Internet. You send e-mail with SMTP and a mail handler receives it on your recipient's behalf. Then the mail is read using POP or IMAP.

Hypertext Transfer Protocol (HTTP) (PORT 80) - It is an application protocol for distributed, collaborative, hypermedia information systems.[1] HTTP is the foundation of data communication for the World Wide Web.

SMTP (Simple mail Transfer Protocol) (PORT 25) - This is a protocol widely used by all Messaging\Emailing servers to communicated and send\receive emails.

Its also a feature to read emails on the server
IMAP (Internet Message Access Protocol) (PORT 143) - allows you to access your email messages wherever you are; much of the time, it is accessed via the Internet. Basically, email messages are stored on servers. Whenever you check your inbox, your email client contacts the server to connect you with your messages. When you read an email message using IMAP, you aren't actually downloading or storing it on your computer; instead, you are reading it off of the server. As a result, it's possible to check your email from several different devices without missing a thing.

- Rancy
kianhowAuthor Commented:
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