With the VERY helpfull support of
dreck I seem to have managed to get it going
I tried the current update (0.93) on the SMTP account dreck supplied me with and I finally could send mail without getting errors
Everyone who has the SMTP issue, upload the new files (if you already running 0.92 (RC2) there is no need to re-import the product .XML!) and try again using "LOGIN" authentication type.
Waiting for feedback now