My question (which is really a feature request I think as I’ve searched and not found an answer yet) is in regards to keeping these in sync, not with mail as such but with settings/rules etc.
As you have purchased a Business license, the settings file can be added on the license server as @gary advised in this thread on that subject, and then automatically pushed to all devices using that license”.
To find out where and how to do that as a paid Business user, go to the VIP support page and login with your registered email address and password and lodge a support ticket.
You can also Sync Rules between computers depending on your Server. See the following eM Client Blog on that subject. If you need any further assistance with Synching Rules to multiple devices, suggest to put that on a ticket.