iOS Apple Mail keeps changing SMTP password

I have set up Mail account using an email address from my own domain. I created an App Password on the email host, and entered the host email address and App Password both the “Incoming M ail Settings” and SMTP settings in the Accounts & Password settings on iPad. All works well the day I set it up. A day later, incoming email works fine, but outgoing email will not work with a error message Mail cannot access the SMTP server. When I check the settings, it is obvious the SMTP password has changed (8 - 10 * instead of 16). Change password back to App Password I luckily saved, outgoing mail goes.

Whatvam I missing?