That's not true, by either the letter of the law or the spirit of it. I own a business, and I post my email publicly because I want people to contact me. Some of those people will be selling me things--I want that! It's true that I end up with a lot of spam as a result, and that sucks, but it's better than never receiving unsolicited business email.

Sending unsolicited email to consumers is, indeed, spam. B2B is different.

EDIT: CANSPAM (US) is a bit ambiguous on this point. (Helpful blog post: http://customer.io/blog/Send-email-without-unsubscribe-link-...) CASL, its Canadian equivalent (I'm Canadian) is very clear on this point, though--unsolicited B2B to a publicly posted email address is a-ok, as long as it's not automated.