Internet Assigned Numbers Authority

                                            Internet Message Access Protocol (IMAP) Capabilities Registry

   Last Updated
   2025-03-18

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   Registries included below

     • IMAP Capabilities
     • IMAP Quota Resource Types

IMAP Capabilities

   Registration Procedure(s)

 IETF Review

   Reference
   [RFC3501][RFC9051]

   Note

 Client implementations compliant with [RFC3501] SHOULD NOT require any
 capability name other than "IMAP4rev1". Client implementations
 compliant with [RFC9051] 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 [RFC9208].

   Available Formats
   [IMG]
   CSV

      Capability Name             Reference
   ACL                    [RFC4314]
   ANNOTATE-EXPERIMENT-1  [RFC5257]
   APPENDLIMIT            [RFC7889]
   AUTH=                  [RFC3501][RFC9051]
   BINARY                 [RFC3516]
   CATENATE               [RFC4469]
   CHILDREN               [RFC3348]
   COMPRESS=DEFLATE       [RFC4978]
   CONDSTORE              [RFC7162]
   CONTEXT=SEARCH         [RFC5267]
   CONTEXT=SORT           [RFC5267]
   CONVERT                [RFC5259]
   CREATE-SPECIAL-USE     [RFC6154]
   ENABLE                 [RFC5161]
   ESEARCH                [RFC4731]
   ESORT                  [RFC5267]
   FILTERS                [RFC5466]
   I18NLEVEL=1            [RFC5255]
   I18NLEVEL=2            [RFC5255]
   ID                     [RFC2971]
   IDLE                   [RFC2177]
   IMAP4REV1              [RFC3501]
   IMAP4REV2              [RFC9051]
   IMAPSIEVE=             [RFC6785]
   INPROGRESS             [RFC9585]
   JMAPACCESS             [RFC9698]
   LANGUAGE               [RFC5255]
   LIST-EXTENDED          [RFC5258]
   LIST-METADATA          [RFC9590]
   LIST-MYRIGHTS          [RFC8440]
   LIST-STATUS            [RFC5819]
   LITERAL+               [RFC7888]
   LITERAL-               [RFC7888]
   LOGIN-REFERRALS        [RFC2221]
   LOGINDISABLED          [RFC3501][RFC9051]
   MAILBOX-REFERRALS      [RFC2193]
   MESSAGELIMIT=          [RFC9738]
   METADATA               [RFC5464]
   METADATA-SERVER        [RFC5464]
   MOVE                   [RFC6851]
   MULTIAPPEND            [RFC3502]
   MULTISEARCH            [RFC7377]
   NAMESPACE              [RFC2342]
   NOTIFY                 [RFC5465]
   OBJECTID               [RFC8474]
   PARTIAL                [RFC9394]
   PREVIEW                [RFC8970]
   QRESYNC                [RFC7162]
   QUOTA                  [RFC9208]
   QUOTA=                 [RFC9208]
   QUOTASET               [RFC9208]
   REPLACE                [RFC8508]
   RIGHTS=                [RFC4314]
   SASL-IR                [RFC4959]
   SAVEDATE               [RFC8514]
   SAVELIMIT=             [RFC9738]
   SEARCH=FUZZY           [RFC6203]
   SEARCHRES              [RFC5182]
   SORT                   [RFC5256]
   SORT=DISPLAY           [RFC5957]
   SPECIAL-USE            [RFC6154]
   STARTTLS               [RFC3501][RFC9051]
   STATUS=SIZE            [RFC8438]
   THREAD                 [RFC5256]
   UIDONLY                [RFC9586]
   UIDPLUS                [RFC4315]
   UNAUTHENTICATE         [RFC8437]
   UNSELECT               [RFC3691]
   URL-PARTIAL            [RFC5550]
   URLAUTH                [RFC4467]
   URLAUTH=BINARY         [RFC5524][RFC Errata 6214]
   UTF8=ACCEPT            [RFC9755]
   UTF8=ALL (OBSOLETE)    [RFC5738][RFC9755]
   UTF8=APPEND (OBSOLETE) [RFC5738][RFC9755]
   UTF8=ONLY              [RFC9755]
   UTF8=USER (OBSOLETE)   [RFC5738][RFC9755]
   WITHIN                 [RFC5032]

IMAP Quota Resource Types

   Registration Procedure(s)

 Specification Required

   Expert(s)

 Alexey Melnikov, Ken Murchison

   Reference
   [RFC9208]

   Available Formats
   [IMG]
   CSV

   Name of the Quota                Description                 Extra required IMAP   Extra optional IMAP      Author         Change    Reference
     Resource Type                                               commands/responses   commands/responses                    Controller
                      The physical space estimate, in units of DELETED-STORAGE STATUS                                                  [RFC9208,
   STORAGE            1024 octets, of the mailboxes governed   request data item and  N/A                 [Alexey_Melnikov] [IESG]     Section 5.1]
                      by the quota root.                       response data item
                      The number of messages stored within the DELETED STATUS request                                                  [RFC9208,
   MESSAGE            mailboxes governed by the quota root.    data item and response N/A                 [Alexey_Melnikov] [IESG]     Section 5.2]
                                                               data item
   MAILBOX            The number of mailboxes governed by the  N/A                    N/A                 [Alexey_Melnikov] [IESG]     [RFC9208,
                      quota root.                                                                                                      Section 5.3]
                      The maximum size of all annotations
   ANNOTATION-STORAGE [RFC5257], in units of 1024 octets,      N/A                    N/A                 [Alexey_Melnikov] [IESG]     [RFC9208,
                      associated with all messages in the                                                                              Section 5.4]
                      mailboxes governed by the quota root.

                                                                 Contact Information

          ID              Name                 Contact URI            Last Updated
   [Alexey_Melnikov] Alexey Melnikov mailto:alexey.melnikov&isode.com 2021-12-09
   [IESG]            IESG            mailto:iesg&ietf.org             2021-12-09

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