The process to change thunderbird password only takes few steps
First, start the Mozilla Thunderbird email program. If you have already changed your email account password on the server, Thunderbird will either display an error message stating that it cannot connect to your account or display a "Enter Password" type dialog. When you see this dialog, just enter your new password and let Thunderbird remember it and you're done. Otherwise, read the rest of this tutorial to see how to change saved passwords.
Once in Thunderbird, click on the "Tools" menu and select "Options" (for Windows and Linux) as shown in the screenshot below.
When the chat option opens, click on the "Security" tab. Then, select the "Passwords" sub-tab to view your saved passwords or change your Master Password. To get a password stored by Thunderbird for a specific email account, click the "Saved passwords" button
Thunderbird will upload a new account that contains all the email files you have chosen to store as password and on disk
To change the password saved in Thunderbird, you must delete it manually; to delete all saved passwords and change them later, click on the "Delete All" button. To change the saved password for a particular email account, select it from the list, and click the "Delete" button: you'll probably have to do it twice for each email account, since Thunderbird keeps it as separate entries. your email password for various scenarios (such as incoming and outgoing mail servers separately, etc.)
Once you have deleted the saved passwords you wanted to change, click on the “Close” button; then close the Options dialog to return to Thunderbird and your emails.
This is how you can change Thunderbird password