On Friday January 21 at 15:48 UTC users observed that the main page https://kolabnow.com/ became unaccessible and reviled an error: 503 – Server unavailable. The webclient (https://kolabnow.com/apps) was still available, but with seriously degraded performance – to the point where the service would give up and reveal the ‘Maintenance’ page.
Also IMAP, SMTP, ActiveSync, and $DAV was impacted by the failing frontends.
The service was unavailable for about 50 minutes, during which time all mails, in and out, were queued. When the service again was available, those mail queues first had to be delivered before new mail could be sent or received. This caused users to experience a delay in the traffic.