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How Email Works


Emails in its simplest form is an electronic message sent from one device to another. With the introduction of mobile phones, tablet computers, social networking sites, e-Commerce, corporate infrastructure, personal communication, etc., the digital world of communication is exploding.

There are many basic components of emails, each one simple, but yet play a very vital role.

Transfer Protocols (Sending) used by MTA (Mail Transport Agent)


SMTP - (Simple Mail Transport Protocol), is the internet standard for sending email. By default, uses TCP port 25 (non-secured) and port 587 for SSL (secured) for sending. SMTP Server are also referred to as Outgoing Mail Server or MTP Server.

Transfer Protocols (Receiving) used by MDA (Mail Delivery Agent)


POP - (Post Office Protocol), supports simple download-and-delete requirements for access to remote mailboxes. Most POP clients have an option to leave email on server after download, email clients using POP generally connect, retrieve all messages, store them on the user's device as new messages, deletes them from the server, and then disconnect.

IMAP - (Internet Message Access Protocol), which is used for coordinating the status of emails (read, deleted, moved) across multiple email clients. With IMAP, a copy of every message is saved on the server, so that this synchronisation task can be completed. In other words, it does everything the simplier POP protocol does and so much more.

Retreiving Mail Performed by MUA (Mail User Agent)


MUA - are software programs which people refer to as their email clients (Outlook, Mozilla, gmail, ymail, hotmail, etc). These clients allow the users to organize, create, read, send and do everything we love to do with email by using the protocols mentioned above.

Putting It all Together


How Email Works Diagram

Source: Unlock The Inbox

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