So me, being the smart-arse I am, rigged up my systems to email me when errors in my webapps occur, from a generic mailbox on our work server.
Today, I get a stack trace out of the blue, and all the systems that I know of are working fine. The email doesn't say what system it comes from, merely that something is wrong with it.
In future, I shall be more courteous. "Hi there, I'm system FOO BAR, "+e.getMessage() and so on and so forth.