Uninstall the old webmail package:
Code:
rm -fr /home/admispconfig/ispconfig/temp/webmail
rm -fr /home/admispconfig/ispconfig/web/webmail
rm -fr /home/admispconfig/ispconfig/web/tools/tools/webmail
and install the new webmail package from ispconfig.org:
http://www.ispconfig.org/downloads/webmail.pkg