Old community - lot of invalid emails

[Sonya*]

Hi,

I have an old community here, grounded about 20 years ago. There are over 250 000 registered users over the time. The nature of the community is that the users are only active for some years and leave then. My issue now is that over the half of email addresses (estimated) are not valid anymore. I would like to "purge" the database setting users with invalid emails on validating to prevent sending emails to them. At the end of the day I need a "clean" database to send out newsletter to valid emails only. What is the best way to achieve it?

Right now I am using G Suite Business to send out and receive e-mails. I pay around 45 Euro monthly. This is my email stats from ACP:

Any advice of what is the best solution in this case? 

Thank you,
Sonya*