Test outgoing email
Setup outgoing email in your moodle instance. (For simplicity, you can use tools for testing outgoing emails such as Mailcatcher or MailHog).
Create some users
Do some actions that result in sending of emails to the users (forgotten password, send messages, etc.)
Verify emails are received by the intended recipients.
Check third party libraries page
Go to [Site administration ► Development ► Third party libraries]
Check the entry for PHPMailer.
Confirm that the version is set to 6.0.7