pfSense

# POP3 - Post Office Protocol version 3 (popular e-mail protocol) - RFC 1939

# Pattern attributes: great veryfast fast

# Protocol groups: mail ietf_internet_standard

# Wiki: http://www.protocolinfo.org/wiki/POP

#

# This pattern has been tested somewhat.

# this is a difficult protocol to match because of the relative lack of 

# distinguishing information.  Read on.

pop3

# this the most conservative pattern.  It should definitely work.

#^(\+ok|-err)

# this pattern assumes that the server says _something_ after +ok or -err

# I think this is probably the way to go.

^(\+ok |-err )

# more that 90% of servers seem to say "pop" after "+ok", but not all.

#^(\+ok .*pop)

# Here's another tack. I think this is my second favorite.

#^(\+ok [\x09-\x0d -~]*(ready|hello|pop|starting)|-err [\x09-\x0d -~]*(invalid|unknown|unimplemented|unrecognized|command))

# this matches the server saying "you have N messages that are M bytes",

# which the client probably asks for early in the session (not tested)

#\+ok [0-9]+ [0-9]+

# some sample servers:

# RFC example:        +OK POP3 server ready <1896.697170952@dbc.mtview.ca.us>

# mail.dreamhost.com: +OK Hello there.

# pop.carleton.edu:   +OK POP3D(*) Server PMDFV6.2.2 at Fri, 12 Sep 2003 19:28:10 -0500 (CDT) (APOP disabled)

# mail.earthlink.net: +OK NGPopper vEL_4_38 at earthlink.net ready <25509.1063412951@falcon>

# *.email.umn.edu:    +OK Cubic Circle's v1.22 1998/04/11 POP3 ready <7d1e0000da67623f@aquamarine.tc.umn.edu>

# mail.yale.edu:      +OK POP3 pantheon-po01 v2002.81 server ready

# mail.gustavus.edu:  +OK POP3 solen v2001.78 server ready

# mail.reed.edu:      +OK POP3 letra.reed.edu v2002.81 server ready

# mail.bowdoin.edu:   +OK mail.bowdoin.edu POP3 service (iPlanet Messaging Server 5.2 HotFix 1.15 (built Apr 28 2003))

# pop.colby.edu:      +OK Qpopper (version 4.0.5) at basalt starting.

# mail.mac.com:       +OK Netscape Messaging Multiplexor ready

# various error strings:

#-ERR Invalid command.

#-ERR invalid command

#-ERR unimplemented

#-ERR Invalid command, try one of: USER name, PASS string, QUIT

#-ERR Unknown AUTHORIZATION state command

#-ERR Unrecognized command

#-ERR Unknown command: "sadf'".