When using an email client, you may hear the terms POP3 (sometimes simply referred to as POP) and IMAP. These terms are used to describe different methods used to retrieve your email.
POP3 connects to a mailbox, fetches the messages and then stores a copy locally on your computer. This is the recommended option when configuring your email client/program.
IMAP stores and arranges your messages on the mail server, where your email client/program lists the headers and retrieves messages by request.
Please note: Because IMAP stores all email on the mail server, it is more likely that your mailbox quota will be filled through normal use.