Tools|Account Settings|{select the account}

At the bottom of the pane listing your accounts, look for Account Actions, and when you click that, look for and click on Remove Account.

Doing this removes the account from Thunderbird. It actually retains the data files associated with the account but removes the account entry and its settings. What's on the server remains untouched - well, at least that is my understanding. Can you provide a link to the help that suggested otherwise?

In theory, unless you encrypt your home folder, a savvy user could find the mail store in your profile and read it. You might want to go a step further and remove the entire profile.

Sorry, but I don't understand your answer. I click on 'Tools' but I don't see any references to 'Account Settings'. Where is this?. I am running Ubuntu. Sandy

The bit in blue above is a link to an article that explains this.

http://kb.mozillazine.org/Menu_differences_in_Windows,_Linux,_and_Mac

But as the mozillazine site often goes offline, I'l telll you that you need to look under Edit|Account Settings in the Linux version of Thunderbird.

However, you could click the account, right-click it, select Settings and then you'll be in the Account Settings page.

In Thunderbird, when in doubt, right-click. ;-)