Mezmo change history: Emails Are Not Being Sent

Mezmo reported a major outage affecting US email alerts and delaying email notifications from 2021-10-28 18:13 UTC to 2021-10-28 23:22 UTC (5 h 9 min). Mezmo attributed it to an incident at email provider Sparkpost; Slack and webhook notifications were unaffected. Email alerting was restored.