21- clean all FIXME
79- support other mailbox format like mh, Mail.app, etc.
87- Add Mail-Followup-To support (see IETF draft)
92- We should use a bit string for Store: -folderTypeForFolderName in order
    to return all the types an IMAP server can return.
93- Support RFC850 (Standard for Interchange of USENET Messages)
94- Add certificates validation for the SSL bundle?
95- support IMAP namespaces (rfc2342)
99- fix quoting bug for big5 mails (mails from Koichi and Toshiro)