Does Gmail support all IMAP features?
Gmail IMAP 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 SSL tunneled connections are supported.
- ENVELOPE responses for email addresses in group syntax (RFC 5322 3.4)
- The \Answered flag is not preserved when a message is moved or a label is added to the message.