Thunder-bird is a commonly using email client for managing emails on both windows and Linux systems. At the beginner level, I was very much confused with removing an email account from the email client Thunder-bird. Here I am explaining the steps with screen shot which gives you a detailed idea about the removal of an account from thunder-bird email client.
Click on the "Display the Thunder-bird menu button" >> Options >> Account Settings >> Account Actions >> Remove Acxcount
Right click the account name >> Settings >> Account Actions >> Remove Acxcount