If you have problems with Horde but SquirrelMail gives you the following message.
“A fatal error has occurred Could not connect to database for SQL SessionHandler. Details have been logged for the administrator.”
Here is what will fix the issue.
ls |grep mysql
If you see nothing after that then type the following
ln -s /var/lib/mysql/mysql.sock
You will probably want to run /scripts/upcp after this to make sure that it updates everything else.