SSL error while sending Email from FME Flow

The error message in the screenshot indicates an SSL error, which again suggests that the FME Flow email configuration is either:

1. Using incorrect security settings for port 587.
2. Lacking proper SSL/TLS handshake due to misconfiguration.

Verify Email configuration in FME Flow, go to System Configuration > Notification Services in the FME Flow web interface, and ensure that the SMTP Host uses the correct SMTP server address, that the port is set to 587, that you use TLS for port 587 (not SSL), and of course enter valid credentials. 

You could also update the config file, making short .json file.​​​​​​ and from the server hosting FME Flow, test the connection to ensure the SMTP server supports TLS on port 587 (openssl s_client -starttls smtp - connect smtp.example.com:587) and look for a successful TLS handshake. If it fails, the issue may be on the SMTP server's side.

In addition. you should also check for certificate issues, especially if your SMTP server requires a specific certificate, ensure it is installed on the FME Flow server, and update or install certificates using your operating system's package manager.

One last thing worth to try, is alternative port testing, if port 587 continues to fail, test using port 465 with SSL enabled. Some SMTP servers use this port instead.