Way back in the early days of the Internet, I found myself as the chief Webmaster in charge of all things Internet for our small weather instruments company, Automated Weather Source. One of the first things that I did was register our domain name aws .com so we could set up an email server. This was rather easy to do, so I added the duty of Postmaster to everything else, and from time to time I would check the mail server to make sure that it was up and running.
A couple months later, I found a bunch of messages in the Undeliverable folder, which was rather unusual. I opened the first one and saw a welcome message to the sales team for AT&T Wireless Systems, gushing over how they had just set up an email server at aws .com, and it would revolutionize their business since they could share all their proprietary pricing information on a daily basis. This was followed by a list of each sales team member and an aws .com email address.
Right away, I contacted our ISP and DNS registrar to ensure that we still owned the aws .com domain. Once I was sure that we were still OK, I sent a polite message to the overzealous AT&T sales guy informing him of his mistake. A week or two later, he sent a message to his sales team (using the aws .com email addresses he had listed earlier), informing them that they were switching all their aws .com addresses to attws .com.
However, the damage was done. Apparently, some folks never bothered updating their address books, as we continued to get undeliverable mail on our email server with confidential discussions of contracts, proposals, and pricing strategies. For a couple of months I continued to forward them back to the attws .com postmaster, then I gave up and just deleted them. A couple years later, I think that we were still getting attws email. I left the company, and for all I know someone is still sending confidential sales forecasts to the weather forecast guys.