How to learn how to inbox?

Hi,

I've spent the last few months leaing programming and have developed an MVP for a marketplace I'd like to start marketing. I wrote a bot in ruby that scrapes all the emails off craigslist and automates mail to them using purchased hotmail accounts. The problem is, I don't know the first thing about how to get to people's inboxes.

Does anyone have any recommendations or suggestions on where / how to lea to inbox?

Thank you!