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