Google, especially Google Corp, is very much that way too. One of my users is currently getting a fair bit of spam because a spammer figured out that if they send a message with envelope sender @google.com, rcpt @gmail.com, google.com MX will accept it, then bounce it with NoSuchUser and gmail will accept it. I spent an hour yesterday looking for a way to contact Google about it, but couldn't find anything. Made harder because most things assume you are talking about gmail or youtube, not google.com itself.
It's pretty shameful that these large companies have no real way to contact them.
It's pretty shameful that these large companies have no real way to contact them.