Interesting question.
If you’re emailing large lists, one potential path is building value-first newsletters in a niche you're passionate about — like tech updates, finance, or local business insights. Over time, you could monetize with relevant tools, sponsorships, or partnerships.
Another indirect way is driving traffic to a blog or landing page with valuable content — and letting the monetization happen there (ads, affiliates, etc.).
Of course, consent and deliverability are huge factors — worth keeping your sender rep clean.