I’ve been getting a ton of CBD expo spam for months. Spamassassin picks up most of it, and Gmail collects the rest in the Spam folder.
However, today one got through so I scrolled down to the unsub link and saw it was sendgrid. I recognise them from previously reporting spam. I have no idea if it made a difference but I like to think it did.
So, despite the prevailing advice that you don’t unsubscribe from spam I clicked unsubscribe. I opted-out of that email, and then I saw the greyed out “View Opt Out Preferences” button.

That’s not exactly the friendliest thing to do, making it look like it isn’t active but I clicked on it and discovered a treasure trove!

This spammer has been busy, but Sendgrid allows you to unsubscribe from them all in one click.

“But Donncha, now the spammer knows your email is real!”
Yeah, it’s been inundated with spam for years already. I’m planning on shutting it down sooner or later anyway because I’ve moved most of my logins to service specific email aliases for easy tracking of spam sources. It’s paid off a couple of times too.