At present, not all servers can handle the IMAP4rev1 proposal. An IMAP client has a choice of downloading only message headers, message headers and bodies but not attachments, or all message components. The client connects to the server, gets the amount of information you specify, and disconnects. IMAP allows for the creation of hierarchical folders on the remote server, where POP3 creates local folders. Messages can be stored, sorted, filtered, and managed on the server, making it possible for users to maintain a system of folders that they can access from multiple computers.
All clients display the same messages.
IMAP contains built-in database capabilities that allow users to define rules for managing mail. The rules are configured according to values appearing in the message headers or in the message bodies and can be as specific as deleting messages from certain users when those messages are older than a specified number of days. Rules can also state that only certain messages will appear in the client.