I spent a day fighting with this last month, trying to setup Outlook 2019 with a Kerio server.
It looks to me like Microsoft has put significant effort into making it hard to use any mail server except Office365.
My understanding is that - no matter what you think you're trying to do, Microsoft:
- tries to login to Office365 (even if you select 'manual configure')
- then looks for your autocomplete configuration
- then lets you try a manual connection
It may be possible to configure an autoconfigure xml file that would let Office365 configure itself for SME -- but maybe not, too.
I did confirm that I could setup the account I needed in Outlook 2016, then export the registry settings for the new account, load them into outlook 2019, fiddle with the account and data files, and get it to work -- but that seems a bit extreme.