By default Xandros Scalix edition runs the Scalix web front-end on port 9090. This is quiet annoying as in most cases the mail server is dedicated and you won't be running any other services on it. Least of all another web service running on port 80. In addition most clients expect just to type in a normal looking url and trying to explain port mappings to their users is just a pain.
Why Xandros decided to go with this as a solution is just plain weird. Anyway its quiet quick to rectify. First you need to edit /etc/apache2/sites-enabled/scalix.conf and change the port the virtual web site listen to from 9090 to port 80. i.e
NameVirtualHost *:80
<VirtualHost *:80>
Next you need to disable the default site configuration. Because Xandros is debian based this is best done by running "a2dissite" and selecting default-000 site to disable. Then do a /etc/init.d/apache2 reload and you can access you webmail via http:/ip-addy/webmail.
BTW -- Just a tip but Scalix web front-end doesn't work in Firefox 3 yet. At least not in the beta version of Firfox 3. This may change once the final version is released.