I recently joined from windows mail to thunderbird as microsoft is replacing it with this terrible new outlook.
I really liked windows mail because of its clean appearance. You had less features and customization but a nice and simple overview.
In particular the arrangement of accounts and folders in Thunderbird seems quite confusing to me. None of the current modes available works well for me.
You always have this bunch of folders open for each account and need to expand and collapse it when changing between the accounts. You can use favorites but whenever a special folder is needed you have to open or add another folder mode to the pane which makes it quite more overloaded.
Im using four mail accounts on a regular basis and I think this was handled really well by windows mail.
You were able to select from your account list and whenever you changed the account just the folders of the current account are displayed (and the default inbox is opened) which feels very natural to me.
You can see this on the image above (german). In the center the account section whith the small white bar on the left, marking the selected account. With the "write mail" button on the top, a mail from this account can be written. At the lower left the folder structure for this mail account is shown with "inbox" selected.
Would be amazing if something like this gets implemented as folder mode for thunderbird ❤️
