POP3 and IMAP are two different protocols (methods) used to access email.
Of the two, IMAP is the better option - and the recommended option - when you need to check your emails from multiple devices, such as a work laptop, a home computer, or a tablet, smartphone, or other mobile device. Tap into your synced (updated) account from any device with IMAP.
POP3 downloads email from a server to a single computer, then deletes it from the server. Because your messages get downloaded to a single computer or device and then deleted from the server, it can appear that mail is missing or disappearing from your Inbox if you try to check your mail from a different computer.
Bottom line: IMAP is the safer option as mail is always stored on the mail server, so if your HD crashes, then you connect to the mail server from a new device and everything will be intact.
DIfferences at a glance
|Flexibility||Can view just message headers, and then choose which messages to download.||Have to download all messages at once.|
|Delete or move a message without having to download it.||Must download all messages.|
|Option to download only the body of a message.||Must download entire message, including attachments.|
|Synchronisation||View messages in all folders.||Only view messages from the Inbox.|
|Changes made via our web interface or email software stay in sync everywhere.||Once downloaded, changes can only be made on local email software.|
|Access messages at home, work, and through the web.||Access messages only from a single device.|
|Safety||All messages kept with multiple redundant copies on our servers||Once downloaded, the message only exists on your local computer. If it crashes, the message is lost.|