11.5. How do I uninstall Enigmail?

In SeaMonkey 1.x: go to OpenPGP → Preferences, click the Uninstall button, then restart SeaMonkey.

In SeaMonkey 2.0 and Thunderbird: go to Tools → Add-ons → Extensions, right-click on Enigmail, choose Uninstall from the context menu, then restart the mailclient.