Re: The way things are going with Office 36x (where x >>> 0)
"We're currently handling about 35 different companies (/O's) and 100+ mail domains aggregated into a single Domino domain. It's actually rather easy to manage all things aside in compared to what would need to be done in Microsoft world."
Not true for at least a decade. Exchange is specifically built to support multiple tenants. You can easily run it as a shared hosted service with multiple tenants that are utterly unaware of each other.