I agree with you. So many companies end up with absolutely terrible unsubscribe code that just flat out doesn't work[1]. With my own server I can just burn a particular email with one line in a file, or I can block their whole domain. I end up having to do this fairly regularly.

I can also choose the message to send in the smtp 5xx error line and so I like to call them names. I know a person never sees it but it makes me feel good knowing my server is cursing out the spammers' servers.

[1] I would venture that roughly 30% to 40% of email unsubscribe links aren't url encoded so that the `+` in the email goes in naked to the url, resulting in the server decoding it into a ` `. Sigh.