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                                              Post Office Protocol version 3 (POP3) Extension Mechanism

Last Updated
        2013-03-13

Note

 The POP3 Extension Mechanism [RFC 2449] updates [RFC 1939] to define a
 mechanism to announce support for optional commands, extensions, and
 unconditional server behavior.  Please see [Section 1 of RFC 2449]  for
 details regarding POP3 Extensions.

Available Formats
        [IMG]
        XML [IMG]
        HTML [IMG]
        TXT

Registries Included Below

  • POP3 Capabilities
  • POP3 Response Codes

POP3 Capabilities

Registration Procedure(s)

             Standards Track or IESG-approved Experimental RFC


Reference
        [RFC 2449]

Available Formats
        [IMG]
        CSV

   CAPA Tag        CAPA Args     Added Cmds           Cmds Affected              List     Diffs         Cmd Valid               References
TOP            none              TOP        none                              both        no    TRANSACTION               [RFC 2449]; [RFC 1939]
USER           none              USER, PASS none                              both        no    AUTHENTICATION            [RFC 2449]; [RFC 1939]
SASL           mech list         AUTH       none                              both        no    AUTHENTICATION            [RFC 2449]; [RFC 5034]
RESP-CODES     none              none       none                              both        no    n/a                       [RFC 2449]
LOGIN-DELAY    secs, USER        none       USER, PASS, APOP, AUTH            both        yes   n/a                       [RFC 2449]
PIPELINING     none              none       all                               both        no    n/a                       [RFC 2449]
EXPIRE         days, NEVER, USER none       none                              both        yes   n/a                       [RFC 2449]
UIDL           none              UIDL       none                              both        no    TRANSACTION               [RFC 2449]; [RFC 1939]
IMPLEMENTATION text              none       none                              TRANS, both no    n/a                       [RFC 2449]; [RFC 1939]
STLS           none              STLS       USER, PASS, CAPA                  both        no    AUTHENTICATION            [RFC 2595]
AUTH-RESP-CODE none              none       none                              both        no    n/a                       [RFC 3206]
UTF8           USER              UTF8       USER, PASS, APOP, LIST, TOP, RETR both        no    AUTHORIZATION             [RFC 6856]
LANG           none              LANG       all                               both        no    AUTHORIZATION TRANSACTION [RFC 6856]

POP3 Response Codes

Registration Procedure(s)

             RFC Specification Required


Reference
        [RFC 2449]

Note

 See [Section 9 of RFC 2449] for details regarding Response Codes.

Available Formats
        [IMG]
        CSV

Response Code Response Types                              Commands                              Reference
LOGIN-DELAY   -ERR           USER[1], PASS, APOP, AUTH                                          [RFC 2449]
IN-USE        -ERR           PASS, APOP, AUTH                                                   [RFC 2449]
SYS/PERM      -ERR           All commands                                                       [RFC 3206]
SYS/TEMP      -ERR           All commands                                                       [RFC 3206]
AUTH          -ERR           Any authentication command including AUTH USER [2], PASS, or APOP. [RFC 3206]
UTF8          -ERR           LIST, TOP, RETR                                                    [RFC 6856]

                                                                      Footnotes

[1] see spec for details
[2] Returning the AUTH response code to the USER command reveals
    to the client that the specified user exists.  It is strongly
    RECOMMENDED that the server not issue this response code to the
    USER command.

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