After 2020.4.1 upgrade, Orchestrator fails to send Alert emails. UiPath.Orchestrator.Core.Exceptions.BadRequestException: Error code - 2600, Message - 'Sending the test mail failed! Original message: An error occurred while attempting to establish an SSL or TLS connection.
Orchestrator tries to use encryption if SMTP server provides one, even if it is not explicitly enabled on the Orchestrator's settings.
This is a known issue on our side, it has been fixed in Orchestrator 20.4.2.