Urbane Tiger wrote:

But what I've noticed is that sometimes Outlook is running as a
Service - you can see that with Process Explorer, can't remember if
it runs under a service host or direct under services

Outlook never runs as a service, as far as I can tell. It's clearly not
listed in the Services console.

I fixed it by installing Dave Levinson's Shutdown addon - apparently
its a common problem for Outlook to be execute out of sight.

Still running after being closed is not the same as running as a service.
It usually means you have a misbehaving add-in that isn't allowing Outlook
to close properly.
--
Brian Tillman [MVP-Outlook]