I just received an email from Yahoo! mail that starts:

We appreciate that you have been with Yahoo! Mail for the past 13 years.

Wow, cool. 1998: before Google, for practical purposes. Before Firefox (though we had Netscape Navigator), before the iMac and the iPod. And perhaps most relevant, before email spam filters had reached maturity.
I was a regular usenet participant, but I unwisely posted under my home email address, resulting in a whole mess of junk mail. I signed up for a Yahoo! mail account explicitly to have a honeypot, an address I wouldn’t mind giving out to marketers (scrupulous and otherwise). And I still use it that way.