alt Hacker NewsThey classify it as "transactional" emails (like what is supposed to be order receipts, shipping updates, etc) and so "decide" they can send you an "order update" to an "existing customer with a business relationship" 6 months later, instead of adding you to the spam list immediately.
I just received a marketing email from Dell, and in the footer they claimed it was a transactional message. The last transaction I made with them was 3 years ago!