I have spent that last month testing more than 50 different lists on smtping, we are data brokers and we are also an email marketing agency with a considerable number of validation on different platform. So far, smtping in terms of quality, quantity and pricing are the most fair on the web for now.
The support is super reactive as well, and the chat option is really really helpful.
I would like to suggest to the team some features to add also, how can I reach you via email guys?