Hi Terry,
Is this a question about sending mail lists or are you only sending general business emails to one customer at a time?
For less than $25/month you can have a small dedicated smtp server for your company hosted within Amazon AWS that is sued for sending general business emails. You'd need to hire someone to create and maintain it, but you would be the only company using your IP address. I think this is one step better than getting a static IP from your ISP. If sending from your ISP works then go for it, but if you continue to have email deliverability issues maybe launching your own server within Amazon would help.
There is a lot more to sending mailing lists than having a mail program and a dedicated IP from your ISP. You will also need to manage your bounce messages and other errors, clean your lists, support and keep the mail server and service upgraded so it doesn't get hacked, and hope that an abuse complaint does not result in your ISP turning off your internet connection for a couple days while they figure out what's going on.
I think it's best leave sending mailing lists to the experts such as
MailChimp.
Additional email newsletter services are listed on our
Email Marketing Reviews page.