Over the last couple of days I've been trying to put Funambol (for those that don't know, Funambol is a mobile messaging server that allows, for instance, data sync, and it's open source) to work and to be accessible "over the air".
Since @work I'm a Microsoft guy, @home I fall into the "the dark side of the force", and use (or at least try since I'm sooooo newbie) linux, in this particular case, Ubuntu.

Getting Funambol to work is extremely easy:
First get a terminal window and download the package:

# sudo -s
# wget http://download.forge.objectweb.org/sync4j/funambol-7.0.6.bin

Then just install:

# sh funambol-7.0.6.bin

Using the default directory for the instalation, start the funambol server:

# /opt/Funambol/bin/funambol start

On your browser you can now type http://localhost:8080, hit Enter and voila, the DS Server page is shown.
Here you can browse to the Web Demo client and loging as a guest.

To manage the Funambol server, we user the Admin applet by executing:

# /opt/Funambol/admin/bin/funamboladmin

After login (File > Login user:admin password:admin), we can now manage the server, and, for now, create a new user, by expanding the tree till we reach the Users node and adding a new user.

So, for completing this first step, all we need to do is install the mobile client. I'm using the Funambol client for windows mobile. Many other clients are available, like for iPod, BlackBerry, Outlook, Java capable phones and of course, the iPhone.

After installing the client and setup the account details, just hit "sync all", and all your data will be placed on the funambol server. (note: I'm assuming that the device used in this step is, for now, can access the local network where the funambol server is located).

Now, I need to configure the server to be accessible "over the air". This was, for me, the hard part since I didnt knew much of Apache and Tomcat.

Since this is a LAMP server, I'll be using the Apache web server as a reversed proxy to the "internal" tomcat server used by Funambol.

Assuming that the domain funambol.domain.tld is poiting to the LAMP server public IP, all we need to do is add a proxy reditection from the Apache to the Tomcat using Apache VirtualHosts:

# gedit /etc/apache2/sites-available/default

In the editor, add a new VirtualHost element like so:

<VirtualHost *:80>
ServerAdmin webmaster@localhost
ServerName funambol.domain.tld

ProxyPass / http://localhost:8080/funambol/
ProxyPassReverse / http://localhost:8080/funambol/

ErrorLog /var/log/apache2/error.log
</VirtualHost>

Now we need to enable the apache proxy be editing the proxy.conf file:

# gedit /etc/apache2/mods-available/proxy.conf

And allowing proxy from all, like the code bellow:
ProxyRequests Off

<Proxy *>
Order deny,allow
Allow from all
</Proxy>

If all went well you will now be able to access the Funambol server throu the client using the funambol.domain.tld url.

Hope that this little tutorial can help you out setting up your own Funambol server.

The next steps, for me, will be getting Funambol to work with Google Calendar and also with Zimbra.