Sort
IMAP4REV2
IMAP4REV1
Performances
Microbenchmark, production reporting data through OpenTelemetry, etc.
Correctness
Behavior tests, Unit tests, RFC compliance tests, Distributed Invariant tests, Fuzzing, etc.
CalDAV
CardDAV
Exchange Active Sync
Microsoft Commitment to Interoperability
Core: MS-ASHTTP - MS-ASCMD - MS-ASWBXML - MS-OXPROTO - MS-ASDTYPES
Features: MS-ASEMAIL - MS-ASCNTC - MS-ASCAL
Additional: autodiscover.xml
IMAP4EXT+
Some extensions that are not part of IMAP4REV1 or IMAP4REV2
JMAP
Sieve
Officiel / Reference Website
Base RFC: RFC5228
Extensions: ToDo
Interop
SASL for example