Downloaded the Debian 4 installer from the Open Source Edition Downloads page.
Unpacked it and started the installer as root

tar xfz zcs-5.0.0_GA_1869.DEBIAN4.0.20071218200820.tgz
cd zcs-5.0.0_GA_1869.DEBIAN4.0.20071218200820
./install.sh

The Zimbra installer checked my system to see if there was an existing installation.
Then it checked for prerequisites and reported the following packages was missing

NPTL...FOUND
sudo...FOUND
libidn1l...FOUND
fetchmail...MISSING
libgmp3c2...MISSING
libxml2...FOUND
libstdc++6...FOUND
openssl...FOUND
libltdl3...MISSING

The installation was cancelled and I had to install the needed packages to continue

apt-get install fetchmail libgmp3c2 libltdl3

Started the install again and now all prerequisites was found.
The installer showed med the following installable packages

zimbra-core
zimbra-ldap
zimbra-logger
zimbra-mta
zimbra-smtp
zimbra-store
zimbra-apache
zimbra-spell
zimbra-proxy

I chose to install all but the zimbra-proxy package.
The installer crashed because the curl package was missing on my system. Installed it

apt-get install curl

and restarted the installer. The installer finished the without further problems.

Importing e-mail messages from my old IMAP server running Dovecot
To import from my old IMAp server I downloaded the imapsync script from http://www.linux-france.org/prj/imapsync/ unpacked it and typed in

./imapsync --syncinternaldates --ssl1 --user1 myOldUser --password1 mySecretPassword --host1 fromMailServer --authmech1 PLAIN --ssl2 --user2 myNedUser@example.com --password2 MyNewSecretpassword --host2 toMailServer.com   --authmech2 LOGIN

I had to install the following packages to run the imapsync script

apt-get install libmail-imapclient-perl
apt-get install libdate-manip-perl

This enabled import of my mail using SSL connection from port 993 on my old mail server to my Zimbra mail server.

I had some problems importing bil mail so I had to increase the mailsize limit from 10MB to 50MB to import all messages. Doing this as user zimbra

zmprov mcf zimbraFileUploadMaxSize 50000000

The Zimbra Administration console is only available from the server itself, that’s why I couldn’t see port 7071 from the Internet. The console is available from https://example.com:7071/zimbraAdmin

Basic usage
These commands can be run as the zimbra user
Stop zimbra

su - zimbra
zmcontrol stop

Start zimbra

zmcontrol start

Running zimbra apache on another port than port 80.
As zimbra user

zmprov ms  zimbraMailPort 8080

This makes it possible to run my own Apache server for my virtual domains.

Running another mysql server
I’ve changed the socket configuration for mysql to have another instance of it running.
Command to login to the mysql console

mysql -p -S /var/run/mysqld/mysqld2.sock