amavisd-new requires Net::Server (Debian package libnet-server-perl) version 0.87 or higher. Net::Server version 0.87 or 0.90 can be used with any version of amavisd-new or Maia Mailguard. If you would like to install version 0.90 from source:

cd /usr/local/src wget http://www.cpan.org/authors/id/R/RH/RHANDOM/Net-Server-0.90.tar.gz tar xzvf Net-Server-0.90.tar.gz cd Net-Server-0.90 perl Makefile.PL make && make test && make install cd

Net::Server 0.93 cannot be used with amavisd-new 2.3.3 or older, in other words in can only be used in version 2.4.0 or newer. Likewise, it can only be used in version 1.0.1 of Maia Mailguard (SVN revision 970 or higher).

cd /usr/local/src wget http://www.cpan.org/authors/id/R/RH/RHANDOM/Net-Server-0.93.tar.gz tar xzvf Net-Server-0.93.tar.gz cd Net-Server-0.93 perl Makefile.PL make && make test && make install cd