User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:68.0) Gecko/20100101 Firefox/68.0

Steps to reproduce:

1. Install Thunderbird
2. Open Thunderbird
3. Configure your first E-Mail-Account if not already done
4. Go to: Hamburger Menu > Settings > Windows Layout > 3 Columns View

Actual results:

The message list remains to be a table but with reduced width. Beside waste of space this causes issues in readability and ergonomics if windows is scaled below 1.920 Pixels in width (e.g. smaller Laptop screen, Tablet (like Surface Go etc.), older wider screens e.g. with only 1.680 pixels width, scaled window ...)

If scaled below 1920 Pixels width:

1. Subject is cutted too early (after 10-15 chars)
2. Sender mail address is cutted too early (after 10-15 chars)
3. Date is cutted too early (year not fully shown)
4. The message list shows far too much items (> 30 at 1050 Pixels height)

If window must be used in even more reduced width, it's not longer usable.

Expected results:

If Thunderbird is used in 3-Column-View-Mode, the message list should switch to a compacted view with only one column like in virtually every other modern mail client. This column should show multiple rows per mail item with the following information:

Left aligned:

• Optional sender avatar
• Sender
• Subject
• Body preview (1-5 lines configurable)

Right aligned:

• Attachment flag
• Priority flag
• Forwarded flag
• Flagged status
• Receive Time/Date

Prominent examples showing how it works are:

• Postbox
• Evolution Mail
• Geary
• Airmail
• Apple Mail
• Outlook
• Outlook Web
• GMail
  ...

Something for the UX people.

This looks like a duplicated of bug 213945.