Canonical list of IMAP Capabilities

Supported

• IDLE command - RFC 2177
• QUOTA - RFC 2087
• NAMESPACE - RFC 2342
• CONDSTORE - RFC 4551
• ENABLE - RFC 5161
• LITERAL+ - RFC 2088
• LOGINDISABLED - RFC 2595, RFC 3501
• STARTTLS - RFC 2595, RFC 3501
• UIDPLUS - RFC 4315
• COMPRESS=DEFLATE - RFC 4978
• XLIST - Supported in Apple iPhone, developed by Google and Apple to define standart folder names like drafts, sent, junk - especially important if they using international names.
• MOVE http://tools.ietf.org/html/draft-krecicki-imap-move
• ID - RFC 2971
• EXTERAL SASL - RFC 4422

Unsupported or partially implement

• Special-Use Mailboxes - RFC 6154
• LOGIN-REFERRALS - RFC 2221, RFC 2193
• MAILBOX-REFERRALS - RFC 2193
• LANGUAGE, I18NLEVEL=1, I18NLEVEL=2 - RFC 5255
• ACL, RIGHTS= - RFC 4314. Currently read-only. Write support (set/modify ACL) has patches for backend and code for frontend
• BINARY - RFC 3516
• CATENATE - RFC 4469
• CONTEXT=SEARCH - RFC 5267
• CONTEXT=SORT - RFC 5267
• ESEARCH - RFC 4731
• ESORT - RFC 5267
• MULTIAPPEND - RFC 3502
• QRESYNC - RFC 5162
• SASL-IR - RFC 4959
• SEARCHRES - RFC 5182
• SORT - RFC 5256
• THREAD - RFC 5256
• UNSELECT - RFC 3691
• URLAUTH - RFC 4467
• WITHIN - RFC 5032
• CHILDREN - RFC 3348
• FILTERS - RFC 5466
• LIST-EXTENDED - RFC 5258
• CONVERT - RFC 5259
• NOTIFY - RFC 5465
• Return STATUS information in extended LIST - RFC 5819