In VA admin site -> Outbound Email configuration you have enabled STARTTLS option but it fails to connect to GWIA.
In gwadmin console check properties of the GWIA object -> GroupWise -> SSL Settings. Cop on your worsktation, for instance, the CRT certificate file used for your GWIA.
Make sure that your GWIA has been configured (Agent Settings tab) to secure SMTP connection (SSL set to Enabled).
Connect now to VA admin interface of Teamworks (port 9443).
Click on Digital Certificate portal. Once in Digital certificates > Keystore: JVM Certificates > File > Import > Trusted Certificate. Use browse botton to navigate to copied GWIA certificate file. Then follow instructions to restart the server.
Once the appliance is back again, you will see in GWIA log screen upgrading to a secure connection whenever any new notification is sent from the Teamworks room.