We are currently using the default port 25 for email configuration.. We have set the communication type as startTLS (optional). We have strangely not been receiving alerts and reports since yesterday morning, though no changes were made.
When I changed the communication type to unencrypted it worked fine and I could get alerts.
What is strange is , as StartTLS was set to optional,why did the server not use unencrypted if startTLS was not loading for the server.
It could have been that no error was kicked back to the server when it sent out the encrypted emails. I would open the server logs and check if there were any email related entries during the time of your issue.