IMAP

The Internet Message Access Protocol (commonly known as IMAP or IMAP4) is an application layer Internet protocol operating on port 143 that allows a local client to access email on a remote server. IMAP4 and POP3 are the two most prevalent Internet standard protocols for email retrieval. Virtually all modern email clients and servers support both.

URI format examples
set spoolfile=imaps://holmes@example.org:password@mail.example.org The above is a .muttrc example for accessing one's Dreamhost mailbox from one's Dreamhost shell account, or any computer in the world.

IMAP NOTIFY
Notify is an IMAP extension which provides for push notifications. Basically, IMAP allows multiple clients to connect to the same IMAP server at once, and when NOTIFY is properly implemented each client gets told of changes made to mailboxes by the other clients.

On these web servers IMAP notify seems to push within a second:
 * Microsoft Exchange
 * Apple's imap for me.com (seems to be based on the netscape code)

On these web servers IMAP notify seems to push between 5-10 seconds:
 * Dovecot (used by DreamHost and pair.com)
 * Google's imap for gmail.

Dreamhost uses the Courier IMAP server on older email servers. It seems to push out updates within 1-5 minutes. Newer DreamHost email servers (homiemail) use Dovecot.