imp (horde) doesn't work

[Debian Mail <debian@sos.ethz.ch>]

I installed horde and imp. Both exited during execution of the
postinst script while configuring the MySQL server. So I went trough
the script and made the necessary stuff myself. Now I made a softlink
to /usr/share/horde/imp/ in my public_html folder. When I try to
access this, I get:


   Warning: Failed opening '/etc/horde/prepend.php3' for inclusion in
   /home/users/stef/public_html/imp/index.php3 on line 1
   Warning: Failed opening '/etc/imp/defaults.php3' for inclusion in
   /home/users/stef/public_html/imp/index.php3 on line 12
   Fatal error: Call to unsupported or undefined function page_open() in
   /home/users/stef/public_html/imp/index.php3 on line 17


Any idea what could be wrong?

Stef