How do I prevent unwanted e-mail ads from reaching me?

Use a service like SpamArrest Basically what it does is it filters mail before it reaches you, new senders not already on your whitelist have to verify they’re human by responding to a CAPTCHA before the mail gets through, and only allows mail to pass if they prove they’re human. Spammers obviously wouldn’t respond because they’re all automated.

Use gmail for your email. They do a remarkably good job at keeping the spam out.

Use gmail and view it though apple mail. Between the two them, they get just about everything. Occasionally I actually log into gmail and am horrified at how much stuff is sent that I don’t have to see. If something does make it through, Apple Mail lets you tag it as junk, and you never see it again, until you clean out the junk folder.