"Feedback" configuration in Geonetwork for sending SMTP emails does not work in Geonetwork

Using 3.12.8-postgres may have a bug in the Feedback configuration for sending emails, as it fails:

`Sending the email to the following server failed : email-smtp.eu-west-1.amazonaws.com:2465. Could not connect to SMTP host: email-smtp.eu-west-1.amazonaws.com, port: 2465, response: -1`

it also fails with 25, 587 or 2587, and with 465 or 2465

Any ideas?

