At one of the places I worked (hotel industry) we had to solicit customers’ email addresses. Customers didn't want to give them out, of course. But I, being just tech savvy enough to be dangerous, was on the custy's side.
I surmised most business class folks have their sales info email addresses: the kind that are set up to kick back advertising every time someone sends a contact.
I made it a point to ask specifically for that email address. I also added any third party email info addresses (priceline.com, expedia.com, hotwire.com) for "deals" on any of those bookings.
Ultimately, I had the great laugh of hearing the sales office swearing about the runaway crossfire.
1) Our automated sales emails were going out
2) Due to their business emails not accepting anything incoming, they were being kicked back to us as undeliverable
3) Which generated more of our automated responses, to infinity
In the end, it locked down the corporate servers handling the volume. Our hotel smartened up and stopped requiring emails.
Am I Satan? Maybe. Mwahahaha!