Hey Emil,
Thanks for the follow-up and for letting me know. In SmarterTrack you cannot create a user using the API and set it to use the active directory at the same time. After creating the user you can use the SetUsersProperties call. Then you can set it to use your AD.
This should allow you to set the Authentication type for the user.
I also edited your post title and tags so if other users have the same question it should be easier for them to find this.
Please let me know if this helps.
Kind Regards,
Zach Sylvester
Software Developer
SmarterTools Inc.
www.smartertools.com