Seems the webmail and webAdmin web.config is being rewritten by MailEnable. I have some redirect URL rewrite rules to redirect http to https.
I think the update to 10.15 may have deleted my rules. If this is what caused it, please do not rewrite the web.config file when applying updates. This is very annoying.
web.config rewritten
Re: web.config rewritten
The web.config being reinstalled also kills HSTS which makes the webgui webpage error out.