Despite the interface removals, Thunderbird 57-60 and beyond and Seamonkey will '''<u>still support</u> these as legacy add-ons <u>if</u> the appropriate modifications are done to the add-on to adapt to the changed interfaces'''.
In addition, Thunderbird will be adding WebExtension support ({{bug|1396172}}) while maintaining "legacy" add-ons and hybrid add-ons. (Note, WebExtension in Thunderbird via {{bug|1396172}} is not yet implmented.)
<br><p>