Changes in Thunderbird 75


  • The onClick event of the action APIs now has information about the active tab and the click event.

    This brings the events into line with browser WebExtensions. For messageDisplayAction, this is a change of behaviour – previously the ID of the active tab was passed as the first argument.

    This change was uplifted to 74 beta 2.


  • The onBeforeSend event now has information about the active tab.

    This change was uplifted to 74 beta 2.

  • The compose API functions can now handle the message body.

    All responses from getComposeDetails calls and onBeforeSend events now return the message body. How you handle this depends on the composition mode (plain text or HTML). For plain text composition mode, the isPlainText field is set to true and plainTextBody should be used. For HTML composition, isPlainText is set to false and body should be used.

    The body field is a string. You should parse this to an HTML document before modifying it, and serialise the document back to a string before calling setComposeDetails. Here’s a sample extension.


  • A new event was added: onNewMailReceived.

    Your extension can now be notified of incoming mail. This is based on the MailServices.mfn.msgsClassified notification.

Bugzilla list of fixed WebExtension API defects in Thunderbird 75.