A user is experiencing issues while sending replies/emails on tickets and the following error message is returned: "Uncaught Exception: Unable to connect with TLS encryption"
One possible cause for this error is that the version of Kayako Classic being used does not support the TLS encryption required by the email server/provider. For instance, very old versions such as 4.70 would encounter issues handling TLS connections. Moreover, even versions from recent years such as 4.93.13 might encounter some problems depending on the TLS encryption used by the email provider.
Therefore, one needs to ensure the Kayako instance is running a recent release and if this is not the case, Upgrade the Kayako Classic Instance to the latest version.
Another possible reason for this behavior is that the mail provider might be experiencing issues with their service as mentioned in TLS Encryption Error when sending Kayako emails using Microsoft Office 365.
Once the instance is upgraded and/or the mail provider issue is sorted out, the connection should work without any issues.