I used to require a "+..." on all emails. Any email that didn't have the "+..." was sent to Spam automagically. My family were whitelisted. I gave up, because too many websites (early on) refused to take the "+..." marker, so I ended up losing too much to Spam. It's easier to just let Google sort it out.
Actually, I am surprised _any_ spammy website these days would even honor the part after the +, and not just directly send to the real mailbox name.