Hotmail & Notes
Sometime around 2005/6 we were banned from automatically forwarding emails to personal accounts (no idea why it was allowed in first place) - as someone had set up forwarding everything to a Hotmail account, one day an email sent the hotmail account over the limit, so a bounce came back including the offending email, this prompty got forwarded to Hotmail growing a bit each time. I am sure you can workout which came off worse a Lotus Notes Server or Hotmail, especially as Notes was storing everything