Finding Product Market Fit with Surveys? Advice?

Has anyone here had success with cold emailing surveys to understand target markets? Is there better way?

Aim:
In following the early advice from The Lean Start Up Playbook, I am attempting to validate perceived importance versus satisfaction for a number of challenges faced by my target customer before building out a product.

Steps so far:
I hired some folks on Upwork to build me an email list of target customers / leads. Meanwhile, I built a survey in google forms and a short email explanation. I had a friend in marketing review all of it and made revisions. I sent the survey to a small chunk of the list (only like 30 so far).

Results:
Haven’t heard a peep.

Next steps:
It probably makes sense to upgrade from my personal email to Mailchimp or something similar to be able to see if anyone is actually opening the emails.

Questions:
In addition to the above questions, what else should I be doing to get the answers I seek? Any articles, interviews, personal suggestions are welcome.

An Aside:
I have reached out to friends / acquaintances / “warm” leads in the target market, and it felt like they were telling me what I wanted to hear, which is why I figured it might be better to try cold leads.

Thanks everyone!