This incident has been resolved. From 16:31 UTC (11:41AM EST) until 18:20 UTC (1:20PM ET), some users received bounceback emails after using @mentions in Greenhouse Recruiting. In any case where this occurred the email did reach its intended recipients, but the email was not logged to the candidate's activity feed.
We apologize for the inconvenience this incident has caused. If you have any questions or concerns, please reach out to us through https://support.greenhouse.io