Sounds exactly like a common website “significantly cheaper” scam, only on Poshmark slash Etsy slash Amazon, where the seller is provided your contact info in order to ship you things. Did they have a history of completed sales? Did you ask any questions and get a response (or not) before purchasing? Someone always ends up being the first rube at any online marketplaces from a scam seller who hasn’t been reported yet, at least when said marketplaces aren’t doing serious in-person identity verification first, and this time you’re the lucky one.

> So the question here is what part of their system is so fundamentally broken that scammers instantly get my email?

Perhaps none. Did the T&Cs permit this disclosure?

Yikes. I wonder if there's a way to differentiate between the bad-seller and the poshmark-is-compromised case.