Plone mod_auth_pubtkt and squirrel mail

[KK CHN]

list,

We are having an intranet site ( intranet.mydomain.com) build on
Plone CMS (plone 3.3 version). I have integrated LDAP plugins for
this site to get authentication using LDAP server (this is
working) .

My requirement is that I am adding a link in the intranet site for
our webmail client , which is a squirrel mail client hosted
( webmail.mydomain.com) . This webmail client uses the same
credentials from the same LDAP server to autthenticate to the IMAP
accounts.

So my issue is here I want only to login to the plone site, when I
click the link for our webmail client it should allow me through,
without asking the login credentials. (single sign on) .

Both the intranet site and webmail client hosted different machines,
under same domain. ( mydomain.com)

webmail.mydoamain.com ( 192.168.39.25 )
intranet.mydomain.com (192.168.39.4)

Please guide me how to accomplish this.

It will be much appreciable your comments and suggestions.

Thanks in advance
KKchn