OLD_SM=/web/old_webmail
SM=/web/webmail
mv $SM $OLD_SM
mkdir $SM
cp -r /usr/local/www/squirrelmail/* $SM
Copy configuration files and preferences dir (if u have config.php_local.php copy that too):
cp $OLD_SM/config/config.php $SM/config/
cp $OLD_SM/config/config.php_local.php $SM/config/
cp $OLD_SM/data/* $SM/data/
Test if new version work… et volia’.
If i forgot something tell me, i’ve used this method many times, it works :).