Yesterday IDNet made some changes and now my android webmail comes up effectively in desktop mode and despite being told there's a setting on the webmail screen to change it that setting isn't there.
Can I recommend k9mail?
https://k9mail.github.io/about.html
I can find Layout options in the Settings screen on the wWebmail. One of those options is List. Not sure if that's what you want, but it seems those are the only options available.