Yahoo! IMAP (imap.mail.yahoo.com)

(from Wikipedia)

It is possible to get direct IMAP access without signing up for paid access nor using software like YPOPs! or FreePOPs. Yahoo! operates IMAP and secure IMAP servers (imap.mail.yahoo.com in particular), which are globally accessible. However they require a specific, non-standard IMAP command to be sent before login is done, namely: “ID ("GUID" "1")”.

Downloads for Windows/Linux and Install Instructions

require 'rubygems'
require 'chilkat'

imap = Chilkat::CkImap.new()

#  Anything unlocks the component and begins a fully-functional 30-day trial.
success = imap.UnlockComponent("Anything for 30-day trial")
if (success != true)
    print imap.lastErrorText() + "\n";
    exit
end

#  Connect to they Yahoo! IMAP server.
success = imap.Connect("imap.mail.yahoo.com")
if (success != true)
    print imap.lastErrorText() + "\n";
    exit
end

#  Send the non-standard ID command...

rawResponse = imap.sendRawCommand("ID (\"GUID\" \"1\")")
if (rawResponse == nil )
    print imap.lastErrorText() + "\n";
    exit
end

#  Login
success = imap.Login("myLogin","myPassword")
if (success != true)
    print imap.lastErrorText() + "\n";
    exit
end

print "Login Success!" + "\n";

#  Select an IMAP mailbox
success = imap.SelectMailbox("Inbox")
if (success != true)
    print imap.lastErrorText() + "\n";
    exit
end

#  Continue with whatever you wish to do...
#  (see other examples..)

#  Disconnect from the IMAP server.
imap.Disconnect()