A Google search of 'aborting handshake because of fatal alert' comes up with the following:

"The signer of the certificate can not be validated on your system. Either the server has a self signed certificate or your system doesn't have the latest server authorities available to it."

The problem seems to be caused by the latest version of the AVG anti-virus software, with scanning of outbound SMTP email somehow causing this fault.

If SMTP scanning is disabled, then email can be sent from the Incisive application without incident.