Although i have used the beta 1151, i am encountering more issues than i care to deal with. Add to that a lack of communications from developer; for me it is time to move on.
i am using an app called MsgFiler which is available in the App Store, it has a currently working beta for Catalina that has NO issues with my usage needs.
i will keep this account alive to see if MailHub ever has a Catalina release, but to be honest, i think this is a dead issue.
Best wishes to all.