Explaining mail protocols

Before delving into how to send emails via the Java Mail API, let's first gain an awareness of the different web protocols related to mailing systems. The three popular protocols used are POP3, IMAP, and SMTP. Both POP3 and IMAP are used to retrieve emails from a mail server, while the SMTP protocol is used to send (deliver) messages.

POP3 and IMAP

POP3 is a protocol used to access an email from the server, download new emails to the client, then delete the emails from the server. In POP3, if you have checked your emails from one device then tried to access them again from another device, you will find that your emails are no longer available, as they were deleted upon accessing them from the first device.

IMAP is also another email access protocol. Unlike POP3, it does not delete original emails from the server, and therefore is suitable for allowing email access from different devices, as your emails are always there on the server. Accordingly, it's the most widely...