Hello there mymozillasupportaccnt. We have read your message We try to help you.

A 2560x1600 screen that’s a quite nice screen. A Dell or a Apple?

Font size settings within Thunderbird.

https://support.mozilla.org/en-US/kb/thunderbird-accessibility-features

http://kb.mozillazine.org/Font_settings_in_Thunderbird

What version of Thunderbird software do you guys use on on your new laptop with win 10?

If it s version 78.01 Most common version at this time.

Menu app icon > Options > Scroll down to the very bottom click on 'Config Editor' button to open 'about:config'

There stands: hello there dragons. Push te button. (Take the risk).

In search type: layout.css.devPixelsPerPx Double left click on that line to open the 'Enter string Value' box so you can edit the Value. The default value will be -1.0

Enter a new number eg: 1.25 or 1.5 or 2.0 or 2.2 click on OK

The impact of text change is direct.(1.25 is oke for normal text format).

Do you wish to install 78.01 Thunderbird version. https://www.thunderbird.net/en-US/thunderbird/78.0.1/releasenotes/

Older versions of Thunderbird software do use add ons for this questions. This add ons where also developed at the same time.

I ve got you a video to solve it. https://youtu.be/klIOX4dsXU4 (Scanned with virustotal).

Greetings Firefox volunteer.

Hello there again.

http://kb.mozillazine.org/Screen_resolution_changes_when_launching_application

You also can look for the resolution setting when starting up your Thunderbird.exe application.

Change this to your needs.

Greetings Firefox volunteer.

This seems to be a bit more complicated than I thought. Let me add more info. I have Win 10 Pro and am using multiple displays. TB looks great on all other screens but it is always tiny on the actual Dell screen. So if i change TB to a larger font, it just makes TB bigger on all screens. The help I need is to make TB bigger, look normal, on the Dell screen so it will look the same, or normal, on all screens.

Thanks again Cullen

Hello there again.

You just might need a tool or add- on?

Dell. Microsoft Windows 10 supports multiple monitors. By setting up multiple monitors, you can increase productivity. When you connect an additional monitor to your Dell computer, Windows 10 will automatically detect the monitor and display the computer's desktop screen. You can then choose how to display the desktop and adjust display settings such as display style, clone mode, extended mode, first screen only or second screen only, screen resolution and color depth settings.

Do you use a docking station for those multiple monitors? Or just one monitor like all other laptops? With usb- c or Thunderbolt.

Some Dell laptops / pc s only just knows how to use two extern monitors. Laptops /pc s like Optiplex.

The first monitor you can asset all settings. The second monitor are just configurations for the settings like colors and adjusting some themes.

If this option exists it will be a Dell option on your computer / monitor itself. Or Thunderbird add-on.

Its not possible in Win 10 to adjust settings for a second monitor. In combination with a dell laptop.(inspirion etc) Also is dpi scaling with going into the directories not a recommended option.

Other setting are available in options like screen adapter. On your Dell laptop with Windows 10 software.

Greetings Firefox volunteer.

PS: My previous laptop was an older Toshiba. I had the exact same setup when using it. Thunderbird looked perfectly normal on the Toshiba screen. The only difference is the new Dell Win 10 Pro Business computer. There is something between Thunderbird & this Dell configuration that is causing the problem.