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

POP3 Capabilities

Registration Procedure(s)

  • Standards Track or IESG-approved Experimental RFC

Reference

Available Formats

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

Note

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

Available Formats

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.