Norton (welknown from the PC world) did write this: The good news is no one has hacked into your account. What you’re experiencing is called “Form spoofing,” and it’s a favorite tool in the spam artillery.
Form-spoofing is annoying, but it’s not dangerous. It’s the sender entering your name and address into the From field in their mail program instead of their own. Outlook, for one, makes this a snap. During the setup process, when asked to enter one’s own email address, spammers choose this option.
Since the name of the game for spammers is hiding their tracks and making sure you receive their mail, from-spoofing is natural. By putting your address in the From field, they obscure the true sender and nearly guarantee that your spam filter won’t block their email. - It's like you can write any returnaddress on an envelope before you drop it into a mailbox.
It's getting real annoying, when you block your own emailaddress, you can risk you can't recieve any mail anymore. They think they can force you to buy their shity stuff when you can't prevent their spam anymore... and they demonstrate at the same time, they know nothing about the human mind and about we would never buy anything, when getting pretty annoyed and angry. Spamcop.net may be the best way to stop this sick minds...