Specifically, currently, you only get 5,000 free mail the first 3 months only. After that, if you continue using, you will have to pay $ 0.80 / 1,000 emails. This price is also quite comfortable when compared to other parties.
The detailed price list is as follows:
Visit Mailgun for more information: https://www.mailgun.com
Mailgun is one of the trusted mailing services I and my friends have used for a long time, they have both excellent mail forwarding and routing services. Unfortunately, it is no longer free.
After checking the list of free SMTP Server services, it seems that SendinBlue is the most attractive when there is a free mail package, but it is limited to 300 mail per day.
Good luck to you for finding the better free SMTP email service!