At Best Database Provider, we partner with several great email database providers. At the risk of playing favourites, I won’t list them here, but feel free to reach out at any time for more info, and we can refer you to a provider that would fit your specific needs.
Additionally, I’ve always found this resource to be useful when it comes to selecting a data provider.
What I will implore you to do is thoroughly vet your data provider, whoever they are. Avoid email scrapers and the providers that use them. You want a list that’s been aggregated over time. Ask for a sample of the list or for an accuracy guarantee to ensure you’re getting the best possible list that aligns with your buyer persona, so you can achieve your campaign goals.