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A user having an email account on a website can easily access his electronic mail by opening the website and logging into his account. But there is another way by which the user can access his electronic mail without opening the website specifically. Post Office Protocol (POP) and Internet Message Access Protocol (IMAP) are two protocols used for accessing email remotely. For this, you need a client like Mozilla Thunderbird which will download your account’s emails onto your computer without you having to open the website. Once the emails are downloaded, they can be viewed on-demand by the user as an when required.

The basic difference between POP and IMAP is that whereas POP deletes the emails on the actual server after downloading them to your computer, IMAP actually works on the actual data stored on the server. Thus, whereas you cannot connect multiple email clients to a POP server (as the email will be deleted once the first client downloads the emails), multiple clients can be connected to an IMAP server and changes made in one client are reflected in real-time in other clients as well. All the changes are synchronized to the IMAP server. Besides this, IMAP also provides the advantage that searches can be made on the server-side without downloading all the emails onto the user’s device.

Whereas POP and IMAP are used for receiving email, Simple Mail Transfer Protocol (SMTP) is used for sending emails. Here the user’s email client connects to the SMTP Server and sends email to the SMTP server. Transmission of an email via SMTP consists of the following steps:

  1. The user’s client sends it to the mail server.
  2. The mail server sends it to a mail transfer agent, which is a program that handles transfer of emails from one server to another.
  3. The mail transfer agent sends it to the destination server by looking up its DNS records.
  4. The recipient server receives it and forwards it to the mail delivery agent, which is a program that handles transfer of emails from the server to user’s inbox.
  5. The mail delivery agent delivers it to the recipient’s email inbox.

For Wikipedia entry on Email, click here.

For Wikipedia entry on POP, click here.

For Wikipedia entry on IMAP, click here.

For Wikipedia entry on SMTP, click here.

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