I spotted this in my IRC feed:
MediaWiki message delivery Delivery of "Share your experience and feedback as a Wikimedian in this global survey" to [[User talk:RStallman (WMF)]] failed with an error code of <code></code>; https://wikimediafoundation.org/wiki/Special:Log/failure
The busted URL is probably a bug in my IRC bot, but the MassMessage failure is real.
https://wikimediafoundation.org/wiki/Special:Log/massmessage has some failures now.