Proofy -- as a service for bulk email verification give you the first 500 checks for free as a new user and give you opportunities to earn up to 50 000 checks for free in user admin panel. If you have any questions feel free to ask support chat. Thank you for your question.
I invite you to check out mailfloss for your use case. The advantage of mailfloss is it handles the bulk email verification for you automatically. All you have to do is connect your Email Service Provider and set some preferences. You only have to do this once, it takes 60 seconds, and requires zero developers. The lite plan will cover you for 10,000 emails per month and only costs $17/month.
I invite you to check out the plans at https://mailfloss.com/pricing/
At DataValidation.com you can purchase 1000 Verification tokens for $7 USD and use those tokens to run your 35-40 emails per day until they run out. You can even invest in a larger package if you want to get an even greater discount. You can find out more here. https://www.datavalidation.com/pricing/
DeBounce is the most affordable in market starting from $0.0003 per check. Moreover, you will receive 100 free credits once you sign up. See pricing here: