You haven't explained the context here so I'll just rewrite it in a semi-formal tone:
I hope everything is okay with you. In relation to your email of September 25th 2011, we are very grateful for you assistance*, cooperation and understanding with regard to our appeal.
I hope to hear good news from you about the people suffering from depression.
* this may not be "assistance" but it's definitely not "favour".
I'm afraid the original isn't very good so it's difficult to get the right context. Therefore, I may have written something that you don't intend in the letter.
Student or Learner