If there is enough interest in this feature request (Email Reports )...
I could write a script to store, retrieve and email this information on a periodic, possibly configurable basis. It would require some hard drive space depending on the number of hosts
The collection script would need to be in a rule that processes all of the hosts you'd want to collect data on and only for level 3 or lower (your preference obviously but setting this any higher than 4 may create performance problems).
For example, this could generate a report via email every day that lists your hosts and the level 3 or lower messages received for those hosts during the last 24 hours. Report frequency could be configurable, but I think I would limit data collection to last 24 hours.
Just a thought, I'm toying around with the idea of creating this for myself, but I don't have a serious enough need to really invest a lot of time into it. If it's something enough people want, I would up the priority a bit just to get it out there.