The following change will be effective with the 13 January 2023 release:
Previously, by default, Shibumi tried to connect to client email servers using TLS when sending email notifications. Secure TLS connections require that both the sending servers and recipient servers use TLS. If the receiving server does not use TLS, Shibumi would still deliver the email notifications, however the connection was not encrypted with TLS.
Starting with release 183.0, Shibumi will only deliver email notifications using TLS. Any client server not configured to use TLS will be blocked and will no longer receive email notifications.