Notice: SMTP connect() failed: You can troubleshoot SMTP connections to find out more about the issue. For example, the connection can fail if one of the SSL certificates was not issued by a trusted Certificate Authority.
Go to Extensions - Plugins and configure the plugin 'System - Debug' with the following settings:
- Allowed Groups: Super Users
Log Priorities: All
Log Categories: mail
Log Almost Everything
Go to Global Configuration - System and turn on the option 'Debug System'. Then go to the Server tab and Mail Settings. Click the button 'Send Test Mail'. If the send function reports an error, you will find the details of the SMTP connection requests and responses from the mail server, including the error codes, from the log file, usually administrator/logs/everything.php.