Thank you!
The account setup screen will re-fill the settings from its preset data if you press Next (and *should* not do that if you press Manual).
However, since this comes up quite often, this logic has been redone for the next update -- the autofill will be only applied during initial account setup.
And btw, I took "mobile-smtp.roadrunner.com" from Android's built-in Email app, is that the wrong server? Please let me know so I can change the preset too.