Rated 5 out of 5 stars

Από τον/την Vako στις Νοέμ. 10, 2018 · μόνιμος σύνδεσμος

Add-ons not marked as compatible with Thunderbird 60 by their authors will be disabled.
This can be reverted via preference: extensions.strictCompatibility
So go to Options->Advanced tab->Config.Editor and search for "extensions.strictCompatibility" then change it from True to False by double clicking on it.