wrong From address after sending E-Mail

Hi
Sending an E-Mail with .NET 4 by assigning the From address like this
Message.From = new System.Net.Mail.MailAddress(FromAddress);
will contain the To address at the place of the From address in the recipients inbox. 
The To address is identical with the username of the credentials.
 
What must be added to have the From address in the ‘From’ part of the recipients inbox?
 
Patrick