Install Horde false.

I am using Debian 4.0 etch I want to install Horde, but virtualmin say i haven't got Mail_Mime, I can't install by "Install Script", So I install manual by "pear install Mail_Mime" But it has error as follow:

pear install Mail_Mime /tmp/glibctestJGJE3k:1:22: error: features.h: No such file or directory pear/Mail_Mime requires PEAR Installer (version >= 1.6.0), installed version is 1.4.11 pear/Mail_mimeDecode requires PEAR Installer (version >= 1.6.0), installed version is 1.4.11 pear/Mail_mimeDecode requires package "pear/Mail_Mime" (version >= 1.4.0, excluded versions: 1.4.0) No valid packages found install failed

I don't know how to install newer version of pear.