re :I've implored, pleaded, offered to pay etc for tuition with Mozilla Community and Support towards that end

No one offers personal one to one, computer to computer tuition. We (other Thunderbird users who volunteer time) only post information via this support forum.

I've been reviewing your past questions to try and find out what problem you are experiencing. But only once have you actually mentioned an issue and it seems to be regarding generic font size throughout Thunderbird. You were given some information. You said "And worse - I upped the print size to 2.5 in the belief and hope that this would solve my Main Tb page but it only made each email enormous......so enormous that I can't undo the 2.5 input because I can't get the "risk" box back!"

It seems you have made the font size too big. So big that trying to use Thunderbird has become difficult and you cannot get to the necessary section as parts of Thunderbird now seem hidden.

I need to know what you did to cause the problem. Did you do this - note I'm presuming you are using version 78* or 91*

• Menu app icon > Options/Preferences > 'General' tab
• Scroll to the bottom
• click on 'Config Editor' button.

You may see a friendly warning accept the risk.

• In search type : pixels
• look for this line: layout.css.devPixelsPerPx

the default value is a negative number: -1.0

• double click on that line to open a small window OR right-click the preference and select 'Modify' which allows you to change the 'Value'

• You can try positive number values such as 1.20 or 1.25 or 1.5 ...............but in your case you entered 2.5
• click on 'OK'

At this point you would instantly see the huge increase in font size, so whilst the same location was visible you would have altered the 2.5 down to perhaps 1.5. However, you had closed that window/tab and now cannot get back to it ? Is this correct? Did you perform that process?

If yes, then you will need to fix directly in the 'prefs.js' file which is in your profile name folder. Try to access it via Thunderbird first.

• Menu app icon > Help > Troubleshooting Information
• Under 'Application Basics' section - about 8th in list is 'Profile Folder' - click on 'Open Folder'

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

• Exit Thunderbird now - this is important.

• Scroll down and locate the 'prefs.js' file.
• Right click on that 'prefs.js' file and select 'Copy'
• Right click anywhere on the desktop area and select 'Paste' - this is a backup copy just in case you make a mistake.

Back to the original prefs.js file -

• right click on the 'prefs.js' file and select to 'Open With' and choose 'Notepad' or a similar simple Text editor program. I think chromebook has one called 'Text'.

• Use 'Edit' > 'Find'
• Type : pixels
• Locate this line: user_pref("layout.css.devPixelsPerPx", "2.5");
• Notice it says 2.5

• Carefully Edit it so it says 1.5 - it should look exactly as it says below
• user_pref("layout.css.devPixelsPerPx", "1.5");

then save the file - File > Save close the window - top right X

Now start Thunderbird.

This should get the general look of Thunderbird to a better font size.

Once this is done we can look at the font settings you have set for reading and writing emails as this is a separate issue.

Hi MacBook pro 16”, OS 11.6, Thunderbird 91.6.1

Can you help get me out of this jam? I may have to abandon Thunderbird which I have been using my entire computer life, upwards of 30 years, to avoid using a web-based email service and archive many of my emails in folders. Till a few days ago, I was using an old (2007) but wonderful Lacie monitor. No longer able to calibrate it to function properly with my printer – crucial for a photographer to control colours, I moved from a 24” 1920x1200 resolution monitor to a 27” 3840x2160 a few days ago. It’s wonderful. However, faced with nearly illegible font size in the Thunderbird interface, I looked to increase the size. Zooming with Command/+ was ok to read incoming messages, but that’s not sufficient. I found the instructions (you can probably see this coming) to alter the config cis (Layout.css.devPixelsper…). I changed the -1 to slighter higher numbers, and didn’t see any difference, so, thinking I could always undo a change, I input a crazy high number – and boom, nothing is visible, just a blank screen except for the 3 red/yellow/green dots and an <. But worse, nothing is accessible via the menu, as everything opens to the same huge screen. Unable to revert, I tried installing a Thunderbird app from my back up, then the Profiles (I copied my MAIL folder first) – no help. Is there something to change in the profiles?

I am desperate to access my archived email folders. Any advice?

IF you inserted a number that was too large then the display will be bad and hard to navigate. You will need to access the profile name folder to fix this issue.

Exit Thunderbird For a MAC - Access profile name' folder, which is here: ~/Library/Thunderbird/Profiles/<Profile name>/

The tilde character (~) refers to the current user's Home folder, so ~/Library is the /Macintosh HD/Users/<username>/Library folder.

In the 'profile name' folder look for 'prefs.js' file. In the 'profile name' folder open the 'prefs.js' file using a simple text editor program like TextEdit. Look for this line:

• user_pref("layout.css.devPixelsPerPx", "x.x");

The x.x will be the crazy high number you inserted.

change it to a smaller number, so it looks like this:

• user_pref("layout.css.devPixelsPerPx", "2.0");

whilst that number may not be the perfect result you desire, it will get access back for you.

• Save the file.

Start Thunderbird.

MAC computers have a lot more pixels in a given space, meaning a pixel is smaller, so whilst using eg: 1.25 on a Windows PC would have instant effect, it would not have much effect on a MAC. So you would need to start by using 3.0 and then try 4.0 then 5.0 etc until you are getting close to a good size then only increase by half, eg: 5.5 or 5.25 etc

Please note: In Config Editor, for 'layout.css.devPixelsPerPx' - after typing the new number you do need to click on the 'tick' icon to save it, then you will see the effect. You do not need to exit the config editor each time as the effect is immediate.

I cannot tell you which is the correct size as I do not have a MAC, but obviously the crazy high number you inserted made it so large the program could not display anything. You need to gradually increase until all is correct.

You are a genius! Thanks for the clear instructions. I seem to have 2 different Library/Thunderbird profiles. I tried the first and there was 1.1, not my crazy number. So I followed your instruction using the ~/Library, etc, and found the correct one with the high number (the 1st screen shot attached). Isn't that strange? Must be a holdover from when I migrated to a new computer in Oct 2021. Much appreciated. Thanks again.