We have the following situation.
Site with 6 servers.
Server5 4.0SP4 with Internet Mail Connector inbound and outbound
Server6 4.0SP4 with Internet Mail Connector outbound
All the other sites with the servers have 5.0 SP1 installed too and are
connected to this site via X.400 connectors.
We are planning to upgrade the last servers with 4.0 that have the IMC
We will start with server6. The plan is to install 5.0SP1 too as on the
We noticed a lot of issues with this version and service pack installed. So
we would like to install 5.0SP2 or go immediately to 5.5SP1. But in that
case, we would have a mix of 5.0SP1, 5.5SP1 and 4.0SP4 ! Will this cause
Can we upgrade from 4.0SP4 to 5.5 ?
If we decide to install 5.0SP2, can it be deinstalled in case of problems ?