I've been using Interspire's self-hosted email marketing platform for years to send autoresponders and high-quality monthly newsletters for clients (they provide me their non opt-in email list). Both have prominent unsubscribe links. I've learned to clean the lists before importing, process bounces and now use SMTP.com (whose IP scored a 97 for the newsletter last month). But, it's the domain and firstname.lastname@example.org email address I'm worried about. It didn't score well through an EmailReach.com test. That domain and email address has been used since 2007 and not until last year did I finally start implementing some best practices. Any suggestions? Should I consider starting over with a new domain or organically improve its score since I'm now doing most things right?
It always starts with the list. You mention 'non opt-in' lists, which is certainly more troublesome than any domain name. Your best course of action is to get a new domain, re-confirm the lists you have (requiring the subscriber to click through in order to stay on), and only accept confirmed opt-in lists moving forward. It will decimate your mailing list in the short term, but long-term eliminate your deliverability concerns and improve ROI.