Thanks for the answer!
That's a bad message. I want to use the strict, because I do not have a flatrate. In the German Forum Nokia has said that N9 has this capability. That's why I bought it.
It is interesting that it works with Gmail without problem. Even with GMX. And the battery lasts for me about 24-36 hours.
Could the problem be solved? Whom should I contact? This is the most important feature for me.