Support for Gmail IMAP extensions has started being added to TIdIMAP4.
The TIdIMAP4SearchKey enum has been updated with new items to support the X-GM-RAW, X-GM-MSGID, X-GM-THRID, and X-GM-LABELS extensions in SEARCH commands issued by the SearchMailBox() and UIDSearchMailBox() methods.
The TIdIMAP4FetchDataItem enum has been updated with new items to support the X-GM-MSGID, X-GM-THRID, and X-GM-LABELS extensions in the FETCH command, however no TIdIMAP methods currently use these new items yet.
Support for the X-GM-LABELS extension in the STORE command has not been implemented yet.