There are a number of PBEM games running through the Discord server, but we are all in favor of people using the GOG forums to start more. I recommend having everyone agree on what Houses they want and what difficulties they want to play at, if they want Universal Warehouse on or off, as well as if they want to play on the Historical or random map (I like the Historical map). You might want to settle on some base rules (no attacking Imperial units if they are not controlled by one of the factions, no attacking Church or League units unless they attack first, etc.).
When you start the game, turn off "Show Tutorials" option but turn PBEM "On". This allows each player to set a password so other players cannot access their turns.
Have fun!