Hi,
I have magento 2 install on ubuntu 18, apache and mysql on a cloud server.
I notice that confirmation emails, and transactional emails are not getting sent.
I checked the var/log for clues.
and this is what I found.
[2019-08-23 07:34:38] main.CRITICAL: Unable to send mail: Unknown error {"exception":"[object] (Magento\\Framework\\Exception\\MailException(code: 0): Unable to send mail: Unknown error at /var/home-directory/vendor/magento/module-email/Model/Transport.php:101, Zend\\Mail\\Transport\\Exception\\RuntimeException(code: 0): Unable to send mail: Unknown error at /var/home-directory/vendor/zendframework/zend-mail/src/Transport/Sendmail.php:305)"} []
[2019-08-23 07:36:33] main.CRITICAL: Unable to send mail: Unknown error {"exception":"[object] (Magento\\Framework\\Exception\\MailException(code: 0): Unable to send mail: Unknown error at /var/home-directory/vendor/magento/module-email/Model/Transport.php:101, Zend\\Mail\\Transport\\Exception\\RuntimeException(code: 0): Unable to send mail: Unknown error at /var/home-directory/vendor/zendframework/zend-mail/src/Transport/Sendmail.php:305)"} []
[2019-08-23 11:04:42] main.CRITICAL: Unable to unserialize value. Error: Syntax error {"exception":"[object] (InvalidArgumentException(code: 0): Unable to unserialize value. Error: Syntax error at /var/home-directory/vendor/magento/framework/Serialize/Serializer/Json.php:39)"} []
[2019-08-23 11:04:44] main.CRITICAL: Unable to unserialize value. Error: Syntax error {"exception":"[object] (InvalidArgumentException(code: 0): Unable to unserialize value. Error: Syntax error at /var/home-directory/vendor/magento/framework/Serialize/Serializer/Json.php:39)"} []'
please, can someone help?