IMAP
IMAP supports both online and offline account access, provides advanced synchronisation features, and lets you view and manage messages without removing them from the server.
Any changes you make are saved and reflected from all locations such as your computer and mobile phone or tablet. However, by default, iMail and Android mail do not synchronize the contents of the device's sent folder with the email box on your server.
POP3
POP3 allows you to read email messages without a constant Internet connection, so you can actually read and manage existing messages while offline.
POP3 downloads the messages from your server to your local computer, phone or tablet. While you can save a copy of the messages on your server, changes made from the local device are not saved on the server.
SMTP
SMTP is sometimes used to send outgoing messages from your e-mail client on your computer, phone or tablet, and to send messages between servers on the Internet.
Which protocol is best?
The protocol that should be used depends on your needs and preferences; however, if you plan on using multiple email clients and devices to access your email account, it is strongly advised that you use the IMAP protocol.
IMAP keeps mail boxes synchronized and allows proper use of hybrid Webmail, email client and device setups. It is also generally faster than POP3, which can be advantageous when reading many messages per day.
