handle WhatsNewDigest emails in this addon rather than via adapter
check for WndSparkPost adapter during setup and fail until it is removed - it is incompatible with this version
change execution order of XF\Admin\Controller\Tools class extension
IMPORTANT: If you have it installed, you must remove the What's New Digest adapter for Sparkpost addon before upgrading SparkPost Mail Transport. The adapter is no longer required and won't work with the latest version of this addon.
