Dear Karl,
This is just a technical P. S. You mentioned "the green background" of my messages. I have been using that backgound because my eyes tolerate it better than the sharp white. And I've just realized that in certain cases the incoming/outgoing messages change their (white or green) colour while in other cases they keep it. Could you please explain to me what this phenomenon depends on? On the setting of my computer? (It says: "Send the answer in the format of the original message.") Of the addressee? Of both of us? My knowledge is too limited to imagine more variations. 
Well, one more, perhaps: which message is the "original" one?...
Best again,