The information below explains the difference between the two most common incoming email protocols, POP and IMAP.
POP stands for Post Office Protocol, and was designed as a simple way to access a remote email server. POP works by downloading your emails from your provider’s mail server, and then marking them for deletion there. This means you can only ever read those email messages in that email client, on that computer. You will not be able to access any previously downloaded emails from any other device, or with any other email client, or through webmail.
Some email clients though like Microsoft Outlook, provides advance settings that would allow you to To enable (or disable) the “Leave a copy of the message on the server”. When this option is enabled, emails will remain on your mail server.
IMAP stands for Internet Message Access Protocol, and was designed specifically to eliminate the limitations of POP.
IMAP allows you to access your emails from any client, and any device, and webmail login at any time, until you delete them. You are always seeing the same emails, no matter how you access your provider’s server.
Since your email is stored on the provider’s server and not locally, you may run into email storage limits, when using IMAP.