With the stock version of the Kmail:
with eclipso.eu provider it is impossible to send smtp messages to provider.
What fails is authentication. The normal settings (which work on TW) are:

whatevermail@eclipso.eu

server: mail@eclipso.de
smtp server: mail.eclipso.de 
587
Plain

With these settings TW does send problem free. But with Leap since about two
days if fails no matter what with "Server error, incorrect authentication data"

The very settings do work w.o. problem on the TW version of kmail. 

I have the doubt it might have been some openssl update or similar that may
have caused this. 
I have not found a way to document the exchange between kmail and the server.
So if you know how to do this, I am taker. 
Thank you.