As a sender, you don't know when #4 happens. Regular people don't check their spam folders. Regular people don't go out of their way to give the sender a head

As a sender, you don't know when #4 happens. Regular people don't check their spam folders. Regular people don't go out of their way to give the sender a head's up that it was classified as spam. I know it happens to me, because I have to verbally follow-up sometimes. The only way you would know if #4 doesn't happen to you, is if you're doing something wrong, like trying to track when people open the email.