Changes

<big>'''Add-ons Guide for Thunderbird 57 and beyond(including version 60)'''</big>

'''Legacy add-ons''': Despite Mozilla core interface removals, Thunderbird 57-60 and Seamonkey will '''<u>still support</u> legacy add-ons <u>if</u> appropriate modifications are done to the add-on author makes modifications to adapt to the changed interfaces'''. The items to be modified are listed below. Core interface (The reasons for these changes and removals have come because is Firefox platform have disabled "legacy" add-ons (in Firefox 57, add-ons which are not based purely on [[WebExtensions]], so Mozilla removed core interfaces.) in Firefox 57. Beyond The picture beyond Thunderbird version 60 is less certain, given the extreme continued high rate of change in Firefox platform code. We will work with add-on authors in the coming months to determine a viable post-60 add-on strategy.

'''WebExtension''': WebExtension does not exist yet in Thunderbird. Thunderbird will be adding WebExtension support (in {{bug|1396172}}) while maintaining "legacy" add-ons and hybrid add-ons.

'''Questions and Help''': Add-on developers can get help in the mozilla.dev.apps.thunderbird newsgroup (the traditional venue) or in maildev mailing list. (see [[Thunderbird/CommunicationChannels#If_you.27re_a_developer]] These forums have more people available to help you than bugzilla and other locations, so please Please ask questions in a forum before filing a bug report in bugzilla. And also Also test and fix your add-on using the latest [http://www.mozilla.org/thunderbird/channel/ beta version] of Thunderbird.