MDPI's IJMS just sent me an email just to say they published a paper and I could read it if I wanted to. Heck, if I wanted to submit an article, they'd be pleased as punch.
I wasn't a reviewer. I had no involvement at any point. This is just spam. Specifically, it's "rent-seeking" behaviour from a publishing group nearly everyone deems "predatory."
See: bit.ly/1yrPredPub
Hilariously, they also include a GPDR statement at the end of their email even though I never gave them my info, and wasn't at all involved in the publishing of this article.
