Gmail IMAP1 is a fairly complete implementation of IMAP, but the following features are currently unsupported:
- \Recent flags on messages.
- untagged FETCH responses.
- Substring search. All searches are assumed to be words.
- There is no SIEVE interface to Gmail filters.
- Only AUTH=XOAUTH and plain-text LOGIN over SSL2 tunneled connections are supported.
- IMAP: IMAP (Internet message access protocol) lets you download messages from Gmail so you can access your mail with a program like Outlook Express or Apple Mail. IMAP syncs the actions you take in Outlook Express or Apple Mail with Gmail so if you read a message in your mail client, it'll be marked as read in Gmail.
- SSL: SSL (secure socket layer) is a way of changing data such as your username and password into code as it travels across the Internet, so that the data will be secure and private.