Let’s take a brief overview of the main mail protocols that allow synchronization and configuration of messages on different platforms, both on PC and via mobile.
POP3 vs IMAP vs Exchange ActiveSync
When you create your e-mail account, you have different possibilities to manage your mail. You can simply use Webmail, by entering the proper url on your web browser then logging in with your credentials and start using the web interface. But if you prefer to use a client software on your PC, or if you want to manage mail also via mobile, synchronizing them on your smartphone or tablet, then you will have to use an email protocol. There are 3 standard one you can choose from: POP3, IMAP and EAS.
POP3 (Post Office Protocol)
POP3 is the oldest protocol (the first POP was created in 1984) and it simply creates a copy of the emails on your PC or Mobile Phone, where the software client is installed. By default, it deletes the messages on the server after synchronization with the client. You can, on the other hand, decide to maintain messages on the server for a certain time.
This method is useful when used on only one device, letting you read your email offline and store them locally deleting them from server.
If you are going to use it on more than one device (choosing not to delete immediately messages on server after sync), you will have duplicated ones, and if you are doing something on them, any changes will not be synced on any other device. In addition, if you delete messages from server after sync, they will result only on one device and not in the others.
IMAP (Internet Message Access Protocol)
IMAP protocol, a little bit younger than POP3, is widely used. The main difference with POP3 is that messages remain on the server even after synchronization with local or mobile email client software.
Since the server is the central repository that IMAP clients sync with, unlike POP3, a user will find the same organization in every client and it is more suitable to be used on more than one device at a time.
Note: when a user deletes a message in the client, this may not delete it from the server immediately. In fact, it only flags the message as deleted, and the server reacts to this based on user-defined specification (e.g., move it to trash, delete the message right-away, …). This is an important point for people who have become accustomed to checking emails from their PCs, phones and tablets in always-connected environments.
As emails remain stored on a remote server, you are restricted to the server’s mailbox size (you can eventually circumvent this by making local archives). Furthermore on mobile phones you should have to modify settings to allow full download of messages from server, since by default IMAP clients will try to reduce the amount of data downloaded only providing most recent messages.
EAS (Microsoft Exchange ActiveSync)
EAS protocol, created by Microsoft in 1996, is based on IMAP, but it adds the opportunity to sync calendar, address book and tasks in addition to email. It is a proprietary protocol, but however, it has been successively ‘licensed’ to other companies and has become a sort of standard for synchronization between groupware and mobile devices.
It offers mail synchronization, plus contacts and calendar on mobile devices. In addition, it makes email sending a bit easier than doing that via SMTP. Emails can always be accessed using any device, since they are stored on a remote server. It is supported by most mobile devices (Android, IOS, Windows Phone).
Not all email services are compatible with this protocol.