Kirk almost always nails these posts and gets to them before me.
Buying a list and trying to get business that way is a long battle that's probably not worth it. He mentions open rates of 15% it's less than that if you buy a list AND it's pretty hard to even send them out, most providers will block you from "spamming people" Even with 15% open rates you'll do lucky to get a 1% click rate and less than that will "convert".
If you do use mail marketing again Kirk is right us it with your customer base, maybe offer a free service for referral to a new customer. Mailchimp or tiny letter is great. Or use Facebook and ask your current customers to "like" you.
Servicevines is an outdoor marketplace where Pro's and customers meet and fall in love.