Improving email deliverability for a client with a poor sender reputation and questionable email acquisition practices requires a comprehensive approach involving ethical considerations, technical implementations, and strategic adjustments. Experts suggest a range of actions, from potentially declining to work with the client due to ethical concerns, to focusing on acquiring payment upfront. Core strategies include eliminating co-registration and purchased lists, concentrating on engaged subscribers, routinely removing inactive users, warming up IP addresses carefully, and diligently authenticating email with DKIM/SPF/DMARC. Monitoring deliverability metrics through tools such as Google Postmaster Tools, creating engaging content, utilizing feedback loops, and adhering to stringent list-cleaning practices are also vital. Ultimately, transitioning to ethical acquisition methods and prioritizing quality over quantity are paramount for long-term success.