Obtaining business emails for email marketing

My first 2 seasons in business, obtaining email addresses did not seem like a big deal. But now with utilizing Jobber recently, I realize the power of having a large email list. With marketing campaigns, the options are endless and effortless; from referral options, lost leads, holiday engagement, the list goes on and on. Ultimately, this could be thousands of money left on the table. With that being said, there has to be an easy way to get a general email list of local businesses instead of digging through each company to find an email. Does anyone know of a way to gather these emails more efficiently?

Thanks

Braxton