By Setting I assume you mean Account Setting. Been there all over the place and can not find a place to enter a password. Also in my7 saved passwords the entry for this account has disappeared. Never had this problem before because there always was a place below the email address to enter a password. That box is no longer there

This is a perennial question, and one I really find quite odd. I assume it is folk trying to be ready.

When you access your account with your old password, then Thunderbird will pop up a dialog asking for the new password with a handy save option immediately under the password. Change done.

Then there is the use of the saved passwords. You access preferences from the menu.

Then search in the preferences for pass o get all the password preferences showing immediately.

If you are using oauth2.0 changing your password is somewhat academic as the authentication will continue to reset until the provider revokes the token used. This generally occurs after a password change, but some don't interrupt the pre-authorised flow.

I just went through a password re-set. I think the missing piece of information that Matt didn't provide which then confused john749 is that in order for the pop-up box asking for the new password to be displayed, the user first has to completely close down and then re-start Thunderbird. Upon the re-start, Thunderbird will try pinging the email server to retrieve messages, fail, and then ask for the new password by displaying the pop-up box with the buttons to select, including Re-set Password.

I always forget this, despite using Thunderbird for more than 15-20 years now! ;-)