I am getting error – SMTP ERROR: Failed to connect to server: Connection refused

Hi,
I am using this plugin, currently I am using gmail id to sent email, and its working fine, but mainly I want to use “Microsoft Exchange Server 2016” to send emails. So I have configured it with “Microsoft Exchange Server” details but it is giving below error when I test it.

SMTP ERROR: Failed to connect to server: Connection refused (111)SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting

Please guide us, what wrong we are doing or any other necessary setting need to be done.

Thanks
John