Drupal8 ->SMTP issue

We have drupal8 setup and having issue with SMTP sending emails. We enabled the debug but anyone know where does it log with detail information?

Error sending e-mail from xxx@xxx.com to xxx@xxx.com: SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting

Error sending email (from xxx@xxx.com to xxx@xxx.com with reply-to not set).

Below suggestion didn't help.

https://www.drupal.org/project/smtp/issues/2622678

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This is resolved. We did a tcpdump to analyize the issue b/w portal and smtp server and adjusted the configuration on SMTP module to resolve it.