Mail processing has now returned to normal. The reboot was required to complete an update to address the issue and after manual intervention to get the server back online mail started processing again.
At this time there are a dozen messages still to be processed. This will take a few minutes at most. Unfortunately as a result of the original issue some purging was required, however, we were careful to protect as much regular email as possible.
Any mail messages being sent to the affected domains will have been queued at the senders server (unless a bounce was already received) and will be delivered in line with the senders server timing schedule. This is normally in and around four hours. All mail received by atom will now be processed in the standard timely manner.
Once again, thank you for your patience.