Back when I was first learning about Tech (early 2000's), I installed a mail server at home and configured it all wrong so I gave up on it. A few days later I noticed that my drive was getting full and didn't know why. This is how I learned about a honeypot, I had left it running, someone had used it for sending spam but since I screwed up the setup all the spam was stuck on my computer with nowhere to route out.
Last time I setup a mail server