Been there, experienced that
I had the same desaster with the adress wdr.org that had been given up by Swiss bank Warburg Dillon Read (now UBS) in the 90th when they got wdr.com, which had been given up by Westdeutscher Rundfunk Köln (German TV)
Every day I got hundreds of porn newsletters, baby pictures, copied computer games ("as this will be illegal soon, I'll send you all my expensive software now!"), movies - and secret stuff of the U.S. police in Chicago about how to get around the people trying to disturb the G7 meeting. The most funny one was a mail of a young guy in India asking his mother to clean up his room as his GF was coming over the next day - and then next day complaining that mom had not done what he had asked for!
At the beginning I told people they were wrong, and the reaction was like it is described here: Ignorance, aggression, and things like "you are a criminal, you are a hacker, I will complain at the IT boss" - and five minutes later an email to postmaster@wdr.org asking to fire this individial that is reading the emails...
The problem was, I only had webspace, it was not my server. That was already expensive enough in those days. So I could not do anything about the mail setup. That hoster was not able to send back mail to non existing addresses. Which made things worse when someone started spamming with faked addresses.
And I only had a modem - that was long before DSL.
So those 20 MB each and every day were really annoying!
Could not get worse? It did. In 2000 Westdeutscher Rundfunk Köln decided they wanted those domains back. So they sued the bank and me over a sum of 500.000.- . Even the bank gave up.
When I told them my whole email was running over those accounts and I did not want my private stuff on TV, they should at least give me 14 days, they said "to prove that we are not in bed with you we need to have your email!" and sent a cease-and-decist letter to hand over everything within 51 hours. Then they lied to Network Solutions and Deutsche Telekom, said they had bought the domain, to steal it before I could download my mail (I was in the middle of moving from one end of Germany to the other in those days).
Later conversation went even further down the belt, when they said, it is my private problem if I use email for private or even intimate topics, as it is a broadcast medium (yes, you have to pay a TV fee for email in Germany by now!).
As a journalist people have to be able to send me information without it being stolen, but I cannot afford it, still paying the depts they caused me in 2000.
So yes, there are people that are too stupid to realize they are sending mails to the wrong person. But there are also people that want to steal email on intention. And the German authorities appreciate this. The Cologne authorities (Staatsanwalt) made a decision, that hijacking and deleting other people's email is legal, as email is not a real thing like a letter on paper. Great! So phishing is legal too, as nobody robs real paper money, eh?
Some people here are quite upset about the activities of state official Wolfgang Schäuble, trying to put trojans on your PC to supervise you. But I don't worry about the police invading my privacy, when public TV already insists on the right to steal my email and broadcast them on TV or put them online to harass me and my family.
See http://www.dl2mcd.de/domaine.html
Some years ago someone said to me, people need 20 years to understand how the internet works. By now I think they will never do so.