Ok, I figured it out myself. If someone is interested:
In the folder: include there is a file: qa-lang-emails.php where all the email text is located. You can change everything but not the parts with the ^ symbols. These are placeholders for the script. You still can take them off if You need to.
For example if You want to change the message text regarding a new answer and just show a link to the answer You need to get rid of : \n\n^open^a_content^close\n\n:
'q_answered_body' => "Your question on ^site_title has just been answered:\n\n^open^a_content^close\n\nYour question was:\n\n^open^q_title^close\n\nIf you like this answer, you may select it as the best:\n\n^url\n\nThank you,\n\n^site_title",
and change it for example to:
'q_answered_body' => "Your question\n\n^open^q_title^close\n\non ^site_title has just been answered. Please see here:\n\n^url\n\nThank you,\n\n^site_title",
Output would be now without the answer text, but still with the link to the site where the user can read the answer and visit that way Your site again. Good for the adsense users as well.