I think these days you pretty much have to have permission to send mails.
Personally I wouldn’t go through with it because:
1) Unsolicited generic mail is a terrible way to market yourself and will do more harm than good.
2) Mailchimp will declare a Fatwa on you if more than a few % unsubscribe from your mailing list stating they never asked for it.
3) Even using Mailchimp you may end up with your domain blacklisted as spam and you’ll have nightmares in the future.
TBH B2B scattergun marketing is a fairly bad idea these days. Better to be more focused. It takes a long time to do it properly, but the quickest way is via LinkedIn. Start with people you really know and have worked with in the past, open a dialogue honestly, don’t hard sell it NEVER works B2B and people talk. If someone doesn’t want or need your product, ask if they know someone who does. Be polite, build networks, offer the fruits of your experience, don’t just spam people or they will never work with you.