Editing Post Office Protocol (section)

==Comparison with IMAP==
The [[Internet Message Access Protocol]] (IMAP) is an alternative and more recent mailbox access protocol. The highlights of differences are:
* POP is a simpler protocol, making implementation easier.
* POP moves the message from the email server to the local computer, although there is usually an option in email clients to leave the messages on the email server as well. IMAP defaults to leaving the message on the email server, simply downloading a local copy.
* POP treats the mailbox as a single store, and has no concept of folders 
* An IMAP client performs complex queries, asking the server for headers, or the bodies of specified messages, or to search for messages meeting certain criteria. Messages in the mail repository can be marked with various status flags (e.g. "deleted" or "answered") and they stay in the repository until explicitly removed by the user—which may not be until a later session. In short: IMAP is designed to permit manipulation of remote mailboxes as if they were local. Depending on the IMAP client implementation and the mail architecture desired by the system manager, the user may save messages directly on the client machine, or save them on the server, or be given the choice of doing either.
* POP provides a completely ''static'' view of the current state of the mailbox, and does not provide a mechanism to show any external changes in state ''during'' the session (the client must reconnect and re-authenticate to get an updated view).
* IMAP provides a ''dynamic'' view, and sends responses for external changes in state, including newly arrived messages, as well as changes made to the mailbox by other concurrently connected clients.
* POP can either retrieve an entire message with the RETR command, and for servers that support it, the headers, as well as a specified number of body lines can be accessed with the TOP command.
* IMAP allows clients to retrieve any of the individual [[MIME]] parts separately – for example, retrieving the plain text without retrieving attached files, or retrieving only one of many attached files.
* IMAP supports flags on the server to keep track of message state: for example, whether or not the message has been read, replied to, forwarded, or deleted.
* POP provides the ability to associate unique identifiers with each message for servers which support the UIDL command. This can be any string of standard visible (non-whitespace) 7-bit ASCII characters up to 70 characters.
* IMAP instead provides unique numerical identifiers for each message, local to each folder, in conjunction with a folder specific UIDVALIDITY number.
* The above two message identification methods (POP UIDL and IMAP UID) are not at all related unless a server implementation which supports both protocols purposely builds the POP3 UIDL string by combining the IMAP UID and UIDVALIDITY values.