Here is what I can tell you after doing some serious research over last few days regarding Scalix on a variety of platforms and the best way to accomplish what I am trying to do (an easy to use MS SBS replacement). Take what you will from it
1. Scalix is using a pre-standard LDAP implementation. This product is old - an evolution of the HP OpenMail product. So linking SME to their LDAP will probably be more trouble than it is worth.
2. You cannot change the LDAP port in the standard Scalix version installers (CE, Small Business, Enterprise).
3. The Community Edition RAW allows you to change LDAP to a different port (they suggest 3890) if you are using an existing instance of LDAP, and redistribute, at the cost of the GUI installer (text only install on CE-R), so perhaps it could be bundled in an RPM with a script to make the needed change to the /etc/redhat-release file, as well as any other changes and then start the installer.
4. If you are looking for ability to host either Scalix Small Business or Enterprise down the road (due to # of Outlook users required), you will need to ask Scalix if you can ugrade CE-Raw to SB or Ent, like you can the standard version of CE, so you retain the modified port, or move it to a different server.
Finally - You WILL need every bit of RAM they say, as I tried it with 416M on an Athlon 850-powered box running SuSE 10.0 OSS for just me and my wife, and it was slow approaching on unusable. The Java rendering of the UI was like watching paint dry. I'd probably suggest no less than 1G or RAM and a 1G Mhz processor or better for a business for snappy performance