Q: How long does it take a new Gmail account to get spam?
A: In my case, one day.
May 26: Create account. Address has never been given out to anyone.
May 27: Receive weird spam in Chinese.
Q: How long does it take for an address, published on the web, to be harvested?
A: In my case, two days.
May 26: Create email address at (non-webmail) domain. Post address on one website.
May 28: Receive weight loss spam and fraudulent lottery notifications, to that address only. And fourteen spams since.
ReturnPath on DMARC+Yahoo
2 days ago