@peter-bis 

Changing the port to 465 and enabling SSL fixed it for me.

  @gabxav 

It's not the connection that's failing, though. It connects just fine on 587 or 465 w/ SSL, authenticates using the credentials given, but fails to send the message because it's not using the "Sender Address" as configured, it's trying to use the username as the sender. The username was given as the auth credentials and that works fine but then that same username should not be attempted to be used again as the sender address, especially since the username is not even in the format of email address.