Best will always be best if it’s more suited to you otherwise it’s not best.
You can check out Best Database Provider which is a B2B database as a service provider.
Disclaimer: I work at UAEPhoneNumber.com
While buying database mailing list you should ideally look at the following parameters:
- Targeting criterion
- Overall data accuracy
- Email deliverability
- Speed of the data delivery
- Overall data freshness
- Cost per contact
If you want to send 1000 emails then aim for at least 90–95% email deliverability so that your domain reputation remains in good shape and your emails land up in INBOX.
On top of that, focus on getting data which is more suited to your targeting criterion instead of simply buying database in bulk without any relevance.
Always personalise your emails so that your email deliverability and open/response rate is high.
Hope that helps!