vCAC 5.2 Error sending email

Hi Guys,

Having an issue getting emails from vCAC 5.2. I can see the following error message from the logs:-

[EML005] ***VSWIS0001 d7bc6229-f52e-4ed1-b453-4f3af937d135: Error sending email using template MachineActivated: The remote certificate is invalid according to the validation procedure.

Can anybody advise how i go about fixing this please?

Regards

Mr G