[AshamedCaptain]

Or just knows about this Gmail trick (it's been 20 years already) and sends spam to your real mailbox.

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.

[thechao]

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.

[aorth]

Good resource on this trick from 2010. It's not Gmail specific.

https://people.cs.rutgers.edu/~watrous/plus-signs-in-email-a...

[gnopgnip]

It's part of RFC 5233 Sieve Email Filtering: Subaddress Extension