Why WordPress Email Not Working Properly?
A big problem for users is not getting emails from the WordPress site. The main reason behind WordPress Email Not Working issue is slow internet speed or server down problem. In order to immediately fix can’t send/receive email from WordPress, you need to install the WP Mail SMTP Plugin. Furthermore, you can annihilate such an email issue by setting up a Subdomain for your website. One more alternative way to fixing the WordPress Email issue is using Gmail or G Suite with WP Mail SMTP.

https://www.wordpresssupport.co/wordpress-email-is-not-working/