You are intermittently encountering the following error "Unable to connect with TLS encryption" when sending ticket reply emails through Office 365:
Uncaught Exception Unable to connect with TLS encryption in .\__swift\thirdparty\SwiftMailer\classes\
This error occurs randomly for customers using O365 SMTP service and often resolves itself without intervention from Kayako Classic support and on some occasions, it has been observed when Microsoft had at the same time published a service degradation bulletin affecting Exchange Online customers. The intermittent nature of the issue indicates that SMTP settings are ok - otherwise, the error would be encountered constantly.
As we are unable to reproduce the issue and based on the above observations, coupled with the fact we have received similar reports from other Kayako Classic customers using O365, this is likely an issue on the Office 365 side therefore we recommend contacting O365 support and share the 'Uncaught Exception: Unable to connect with TLS encryption' error message with them for further assistance.