Display text attachments inline in Thunderbird 68 and later

Apparently there has been a change in Thunderbird 68 so it no longer displays text attachments inline even though View -> Display Attachements Inline is turned on.

There is a solution to this though:

  • Open Tools -> Options
  • Select the Advanced page
  • Switch to the General tab
  • Start the Config editor (button on the bottom right)
  • Press “I accept the risk”
  • change the “mail.inline_attachments.text” value to true

Source: Mozilla Support page