You’re going to have to use an external service for email perhaps connected to something like Postfix or just using the email provider’s API - something else to think of if you just need something on your phone as a message / reminder is to use KDE Connect like in this tutorial https://doronbehar.com/articles/using-kdeconnect-to-comfortably-send-sms-messages-from-the-shell/
What issues are you having with your reverse proxy? Home Assistant is light-years ahead of any other option