I finally had to change the configuration to
SMTP Host: smtp.gmail.com
Port: 587
Authentication: Yes (checked)
User Name: mygmailusername@gmail.com
Pass : mygmailpass
Protocol: smtp (or smtps; both work for me)
Address all email from server will come from: mygmailusername@gmail.com
Use Start TLS: Yes (checked)
Use SSL: Yes (checked)
Now Pentaho 5.0.1 BiServer Can send emails via gmail smtp. Works like a charm