I had an incident the other day where the server logs were being filled with log statements from the Event-task after upgrading a server from Domino 5.0.x to Domino 6.5.4FP1. Once the Event-task started the server console, and hence the log, was filled with log statements saying “Event Failed to send mail to .Notes.Administrator.IHI: User %a not listed in Domino Directory”. There would be around 10 lines per second in the log until the task was terminated.
The quick fix was to quit the Event-task until we could figure out what was happening. After some research it turned out to be an Event-handler document where the Notification type field was empty. It should have been set to “Mail” but for some reason it was empty.
After recreating the event-handler document the issue dissapeared and we could start the Event-task again. A simple fix but not the most obvious error message I have seen.