Hi Frederic,
This type of setup is not currently supported. SmarterMail was not designed for clustering and only supports "load balancing" in terms of using
Failover for a hot standby, where two installations are installed using a centralized data location, but only one mail server is active at a time. Aside from when using Failover, we don't recommend using two mail servers on the same server. Because they can't share the same IPs or ports, one server would be without the standard SMTP port 25.
Hope this helps!
Andrea Free
SmarterTools Inc.
877-357-6278
www.smartertools.com