troubleshooting fonts and layout

Sometimes when composing / reading emails, fonts or colors do not turn out as expected. This is hard to troubleshoot for us but you can use the built in tools of Thunderbird to investigate.

If you need to find out what causes the font "look" on a specific section in your emails, open Tools / Developer Tools > Developer Toolbox on the Thunderbird main menu (or press CTRL+SHIFT+I):

starting inspector

(1) Next, click on the "inspector" tab:

starting inspector

(2) optional step - you only need this if you want to click in Composer or a separate "single message window" - select a target document. By default this is the mail 3pane (messenger.xul). To investigate the composer window, pick messengercompose.xul

target document selector

(3) Picker
use this to select what you are interested in with your mouse. regions of interest will be highlighted with a red frame.

(4) Click on the writing on the page in composer / preview

On the left of Inspector, you see the "document tree" - the different parts that make up your email - click any element to select a different paragraph which will be highlighted on screen

On the right hand of the screen you can select different views:


this shows all style rules that apply to the selected element

rules section

If a rule is overridden by another, it will be "crossed out":
overridden styles

You can filter for specific rules with the "Filter Styles" box on top:

filter style rules

You can try out other values by double-clicking the values of ach rule and then typing over. Make sure to transfer the new rules to your template.

Computed Styles

Shows only the styles that "survive" in the hierarchy of styles

computed styles section


This section deals mainly with positioning of the element on screen:

layout section