Magento 2.3.6: Order email is sending but Customer Account create/forgot password email not sending?

Question

We have checked order email is sending proper,when we tried to create new customer or forgot password that time email is not getting. when we have checked in exception.log file we have got the below error.

main.CRITICAL: Unable to send mail: Unknown error {"exception":"[object] (Magento\\Framework\\Exception\\MailException(code: 0): Unable to send mail: Unknown error at /vendor/magento/module-email/Model/Transport.php:103, Laminas\\Mail\\Transport\\Exception\\RuntimeException(code: 0): Unable to send mail: Unknown error at /vendor/laminas/laminas-mail/src/Transport/Sendmail.php:304)"} []

Thank's in Advance,