after setting up SMTP extension ,when send test mail giving error "Unable to send mail:unknown error" and in exception log gives bellow exception.
" main.CRITICAL: Unable to send mail: Unknown error {"exception":"[object] (Magento\Framework\Exception\MailException(code: 0): Unable to send mail: Unknown error at /var/www/magento/app/code/Magento/Email/Model/Transport.php:104, Laminas\Mail\Transport\Exception\RuntimeException(code: 0): Unable to send mail: Unknown error at /var/www/magento/vendor/laminas/laminas-mail/src/Transport/Sendmail.php:306)"} [] "
what would be the reason, and how could I get out of this.. Thank you.