The solution I have found is to click the box in upper right to expand thunderbird to full screen prior to clicking tools>message filters. Also, the match window can be reduced if that helps.

I use resolution 1920 x 1080 and scale 100%

In windows search type : resolution select 'change the resolution of the display'

What is the computer 'screen resolution' and 'scale' percentage?

I've located a bug report which seems to discuss this issue, so if I have some info to tell them about you problem it may help get things sorted.

In 128.10.0

I have found you can resize the 'Message Filters' window but not the 'Filter Rules' window where you create the filter.

In beta 139.0b3

I can increase the width and height of the 'Filter Rules' window but it does have a minimum, so you cannot reduce beyond that preset size.

bug report: https://bugzilla.mozilla.org/show_bug.cgi?id=1879791

I use resolution 1920 x 1080 and scale 100% What is the computer 'screen resolution' and 'scale' percentage?

Thank you for your reply. I use 1920 x 1080 and scale 125%. Some apps don't like that scaling and Some of the things I use are abondonware so the scaling affects them. I started computer and changed scaling to 100% before starting Thunderbird but still window extends below bottom of screen.

Yes; I saw and tried to resize the filter ruless but this doesn't change the overall size of the window. You are correct, it has a minimum size that you cannot go below.

I am a LOOONNNGGGG time user of Thunderbird I wonder if there is a way to reset the config file back to default. I made the text font smaller in the General settings & Advanced settings, but this had no effect on the Add Message Filter window.

In that image, I notice the top title bar font is a lot smaller than the rest of the font. I'm not seeing that difference but can you check a setting because I know this does effect everything in Thunderbird.

• In Settings > General
• Scroll to bottom and click on 'Config Editor'
• In search type: pixel
• Look for: layout.css.devPixelsPerPx

It should have a negative number: -1.0 If it has anything else then click on the 'Reset' curved arrow on the right OR click on the pencil icon , remove all content and then type : -1.0 and click on the tick icon to save. Then reopen the Message Filters and click on New

Did this help ?

'

• Look for: layout.css.devPixelsPerPx

It should have a negative number: -1.0

Yes that resolved the problem. I had changed that entry to -1.7 to enlarge the text used in the UI. It is a bit small for these old eyes. Thank you for your help!!

Good to hear we solved the initial issue. Font size in Thunderbird can be managed via: Menu app icon (3 lines) > Font Size > click on the + sign to increase font size in the UI. Repeat the clicks to increase the default 12px to a higher number so it suits your requirements.

You can also use the 'Density' option to increase the distance between items in Folder Pane and Message List. There are three options - Compact, Default and Relaxed

I don't see Config Editor in Settings, General...

I don't see Config Editor in Settings, General...

It's at the very bottom on the right side. You have to scroll down, it will not be visible if you just select 'Settings > General'. When you scroll down in the 'General' option, the last section is called 'Network & Disk Space' and the last sub section in that area is called 'Indexing' Below that on the right is a button called 'Config Editor' Click on that button and it opens in a new tab which is called 'Advanced Preferences'.

I've tried all the above. Still have the problem. A possibly helpful detail: On my win10 pc running tbird 68.10.07485 it works fine. On my win11 pc running tbird 142.0 it DOES NOT work. Why doesn't this window have minimize/full screen/close buttons? new info: I tried resizing with arrows on edge of window, went to 1/2 size then 1/4 then DISAPPEARED! Now get error tone with any action, like window is still open but can't be seen. I guess I'll try to close with task manager. Tbird is back but still have message filter window problem.

I've tried all the above. Still have the problem. A possibly helpful detail: On my win10 pc running tbird 68.10.07485 it works fine. On my win11 pc running tbird 142.0 it DOES NOT work.

Win 11 is probably not using the same screen resolution nor scale as the win10. If you use a scaling that is greater than 100 per cent, it means it's acting like a zoom thus forcing the actual pixel size to be greater. So forcing the window to be larger. Please post/upload an image to this forum question showing the win 11 screen resolution and scale settings.

Why doesn't this window have minimize/full screen/close buttons?

Not required if all settings are correct.

new info: I tried resizing with arrows on edge of window, went to 1/2 size then 1/4 then DISAPPEARED! Now get error tone with any action, like window is still open but can't be seen. I guess I'll try to close with task manager. Tbird is back but still have message filter window problem.

Please do this first as it should reset all the defaults.

• In Thunderbird
• Help > Troubleshooting Information
• Under 'Application Basics' - half way down - Profile Folder - click on 'Open Folder'

A new window opens showing the contents of your 'profile name' folder.

• Exit Thunderbird now - this is important
• Make sure all Thunderbird is closed via Task Manager

Look for and delete the following two files.

• session.json
• xulstore.json

• Start Thunderbird.

Are you talking about the 'Message Filters' window or the 'Filter Rules' window or both? For both of those windows, the height and width can be adjusted by using arows on edges of window. But they can only be reduced to a set minimum.

Please post an image showing what you currently have got set up for this preference:

• layout.css.devPixelsPerPx