Will be looking to do the same this winter, will then search for more solutions. For now I see this: ‘cPanel E-Mail Manager’ https://wordpress.org/plugins/cpanel-e-mail-manager/ … ‘manage e-mail accounts and mailing lists hosted on cPanel from the WordPress interface…. create and manage e-mail accounts not linked to current WordPress users’. Obviously — test. Possibly not automated in the way you wish. But might be workable for initial growth? I am with an inexpensive basic shared host that allows unlimited cPanel email accounts (although expect would eventually run into slowdowns). Thinking that once proven, should the need arise, I can migrate to the more expensive in-house dedicated server. All else being equal, staying in-house would minimize disruptions.
Please share back if you find an email creation solution that would fit a small unincorporated community.