If you want to change the account password, that must be done on the account online, not with Thunderbird. If you have a new password for the account, Thunderbird will normally post that the current password doesn't work and to enter a new one. If you have a password and want to replace what thunderbird shows, you can do that by these steps: - settings>privacy&security - click 'saved passwords' and then 'show passwords' - now highlight the desired row, right-click, and select 'edit password' - there is one row for incoming and one for outgoing, so possibly need to change both. -