I’m not sure about the e-mail which, in itself, looks suspect to me. What does any of this have to do with that company? I see no reference to them in the image you posted.
Anyway, I suffered a similar issue with a couple of sites a few years back. My .htaccess file had been altered, my file permissions changed and an additional directory uploaded to the site. I would suggest you start by looking for something along those lines.
@dklynn wrote a guide to recovering from a hacking attack, which should help you sort thoings out: