Internet Message Access Protocol (IMAP) Capabilities Registry

Last Updated

2026-08-04

Available Formats

XML
HTML
TXT

Registries Included Below

• IMAP Capabilities
• IMAP Quota Resource Types

IMAP Capabilities

Registration Procedure(s)

IETF Review

Reference

[RFC 3501][RFC 9051]

Note

Client implementations compliant with [RFC 3501] SHOULD NOT require any 
capability name other than "IMAP4rev1". Client implementations 
compliant with [RFC 9051] SHOULD NOT require any capability name other 
than "IMAP4rev2", and possibly "STARTTLS" and "LOGINDISABLED" (on a 
cleartext port). All client implementations MUST ignore any unknown 
capability names.

The prefix "QUOTA=RES-" is reserved per [RFC9208, Section 9.1].
See Section 9.2 of that document for values that follow this prefix.

All other capabilities starting with the "QUOTA=" prefix are reserved 
for future IETF Stream extensions to [RFC 9208].

Available Formats

CSV

IMAP Quota Resource Types

Registration Procedure(s)

Specification Required

Expert(s)

Alexey Melnikov, Ken Murchison

Reference

[RFC 9208]

Available Formats

CSV

Contact Information