I was brought on to help with that since I've been working with a ton of companies for years in the installation field. There's also a bit of manual grind happening behind the scenes to reach out to a lot of companies, check their sites for jobs, and searching more conventional job boards for jobs that are appropriate but would be lost in the noise on those sites.
And how is my email handled when subscribing?
Seems to be some kind of twitter related email list service?
We use Mailchimp for that. It's a pretty standard tool for mailing lists, used by everyone from companies to blogs to websites like InteractiveJobs.io. I don't believe there's any Twitter-related email service (unless Twitter bought Mailchimp?) or link to Twitter. I don't even think InteractiveJobs has a twitter account yet haha.
Will my email be shared or sold to the whole wide world of internetz?
No, this was another reason I was brought on, because I've been running my blog http://Elburz.io and it's newsletter for ~2 years now (iirc) and I definitely respect everyone on my list (as I work with many of them regularly). So your email is safe.