How do I know you're spamming?

There are a number of reasons I know that mail coming into my mailbox is spam.

1. I get 15 copies. There are a lot of spammers out there who buy and scrape addresses and don’t do even the simplest of de-duping. Send multiple copies to a single address, you’re probably spamming.
2. I get mail to a non-tagged address. I use tags for every signup, and have done since mid-1999 or so. If I get commercial email to a non-tagged address, I know it’s spam.
3. I get to a tagged address from someone it wasn’t given to. As above, the tags remind me who was given my email address. If mail comes into a tagged address and it wasn’t given to the sender, then I know the mail is spam.
4. I get mail to a poorly harvested address. Another subset of the tagged addresses, there are a couple badly written web harvesters out there which add random characters onto the end of my tags. So I get mail to -infon@ and -infonn@ and -infonnn@ addresses, and I know the sender is spamming.
5. Someone attempts to send mail to an address that never existed at my domain. Even better, I don’t have to receive the mail for this one. If you attempt to send mail to a non-existent user here, I know without even looking that the mail was not asked for.

Am I wrong?