Why is Craft CMS attempting to connect with SSL3 When either of two of our admin logins attempt to add a new admin user and select to send an activation email, we get this error message: 


  Internal Server Error  stream_socket_enable_crypto(): SSL operation failed with code 1. OpenSSL Error messages: error:14090086:SSL routines:ssl3_get_server_certificate:certificate verify failed


Why is Craft CMS attempting to connect with SSL3 which is intentionally disabled at the server level due to known vulnerabilities?
The error is coming from when Craft tries to send out an activation email for the new user.

In Craft's email settings (Settings->Email), you're telling Craft to connect to your email provider over SSL (TLS), but it looks like your local OpenSSL certificate config is setup improperly on your box.

More info here: https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting#php-56-certificate-verification-failure

I definitely wouldn't recommend their workaround of disabling SSL certificate verification as that opens up a slew of security issues, but would fix the local OpenSSL configuration.