With inline spell checking, you might correct errors immediately as you pop in.

To have Mozilla Thunderbird check the spelling in emails as you write them:

Go to theThunderbirdmenu and selectPreferences.

UnderSpelling, select theEnable spellcheck as you typecheck box.

Preferences under the Thunderbird menu

To change the spellcheck dictionary, select theLanguagedrop-down menu, and choose an option.

The Composition heading in Thunderbird Preferences

The “Enable spellcheck as you type” option

The Language menu for spelling

The “Spellcheck As You Type” toggle under Options in Thunderbird