New users can use so-called temporary mail or mail that will cease to exist.
This may be done by bots, or someone may want to harm forum/site etc.
Should I send emails to everyone?
Or maybe you/we can protect yourself somehow?
i.e. any verification message after 2 weeks does the email address still exist?
or automatic deletion of sending messages to those who, for example, had 5 bounces a week?
Or sending an e-mail notification only to users with a given badge (awarded manually or with some merit) ?