| Elective Proposed protocols were
discussed and agreed to, but their application has never come into
wide use. This may be due to the lack of wide need for the specific
application (RFC-937, The Post Office Protocol)...
- E.
Krol; The
Hitchhikers Guide to the Internet; RFC 1118; Sept. 1989. |
POP3 has become the most common email client connection protocol.
Your email client talks to your email
server to send it commands to login, get mail status, and send and receive email.
The most common protocol used by email clients to communicate with email
servers
is the Post Office Protocol, first defined in RFC
918 with Version 2 published as RFC
937, and POP Version 3 published as RFC
1725.
The POP3 protocol enables any email program anywhere
on the Internet to connect to any email server to perform the usual email functions,
such as reading and sending, as long as they have a valid account and password.
POP3
is an open Internet standard. The common POP3 commands and responses are listed
in the following table:
| Command
| Responses
|
| getwelcome
() | Gets
the greeting from the server. |
|
user (username) |
Login with a username. If valid username, server
will respond with request for password. |
|
pass_ (password) |
Send password. If valid, server response will be
two numbers, message count and mailbox size. |
|
stat () |
Get the mailbox status. Response is two numbers,
message count and mailbox size. |
|
list ([message]) |
Get list of messages. An option "message" gets
information on a specific message. |
|
retr (message) |
Get message number "message". |
| dele (message)
| Delete
message number "message". |
|
rset () |
Remove all deleted message markings. |
| noop ()
| No operation.
Do nothing. Really. Needed in unusual programming situations. |
| quit ()
| Quit. Commits
all changes, unlocks the mailbox, and ends the server connection. |
| top (message,
lines) | Gets
just the first "lines" number of lines of message number "message". Useful on
low bandwidth lines to get just the first part of long messages. |
| uidl ([message])
| Gets
a unique id list -- a message digest including unique ids. The option gets the
unique id for the specific message "message". |
You can Telnet into your email provider on port 110 and
exchange POP3 commands with your server just as though you were an email application.
Resources. The following resources provide more information about POP3:
- RFC
1939; "Post Office Protocol -- Version 3"; J. Myers, M. Rose; May
1996.
- RFC
1957; "Some Observations on Implementations of the Post Office Protocol";
R. Nelson; June 1996.
- RFC
2449; "POP3 Extension Mechanism"; R. Gellens, C. Newman, L. Lundblade; November
1998.