Mozilla Thunderbird by default adds the outgoing email addresses to address book. But if you want to disable the automatic addition of outgoing email address then you can use the Thunderbird Options menu. To turn off this feature, click the Tools menu and select Options from the menu list.
Navigate to Composition tab and then select the Addressing sub tab. This would display the following options.
Un mark the checkbox with label as Automatically add outgoing e-mail addresses to my:. And then click OK button to confirm and save the changes.