Firstly thank you Robilaur for this great post, I have been trying for a while to sort this. I hope you do not mind but may I make some additions to your post that may help others that are trying to achieve this and also enable Squirrelmail over HTTPS.
firstly I have posted my system spec so that if any one has similar then they will now that this works:
Debian 5 Lenny
ISPConfig 3 RC2
Falkos (Perfect server setup for the above operating system)
I followed Robilaurs instructions but just to clarify some things.
ln -s /usr/share/squirrelmail/* :/var/clients/client(nr)/web(nr)/web
On a Dabian system you have to include /www in the symlink.
ln -s /usr/share/squirrelmail/* :/var/www/clients/client(nr)/web(nr)/web
Also following Squirellmail's recommendations the command:
chmod +x /var/lib/squirrelmail/*
chmod 775 /var/lib/squirrelmail/
And you should also change the permissions of the users .pref folder otherwise you will get an error when trying to log in
So change the .pref folder to:
chmod 664 firstname.lastname@example.org
Now if you enable a site to have SSL then create an SSL certificate for it.
now create a redirect by selecting redirect type (R) and redirecting to Https://webmail.yourdomain.co.uk
. This means that if a user types in Http by accident it will auto direct to Https.
You can now delete the old /webmail folder as it is no longer used.
rm -r /var/www/webmail
That's it.... just for cleanliness sake only, restart Apache just to be on the safe side
I hope this clarifies a few things and also helps out others in the same boat.