Please make it so that when such mass messages are sent, wikis can receive them in their fallback language if their main one is not available.
(Please also add other tags if relevant.)
Affected projects: multilingual Wikimedia projects, mainly MetaWiki
Pre-deployment testing: local testing by devs
Post-deployment testing: try sending out a translatable page as a mass message, on MetaWiki, to different projects, on pages in different languages, with also testing fallbacks
Added support for sending multilingual pages–using fallback languages if necessary–to the Mass Message extension