Distorted .obj Export Whenever I export a mesh, wich is just a tiny bit complex from blender to an .obj file, some parts of the mesh are ending up wierdly distorted. The only solution I found is to check "triangulate faces" at the export options.
But shouldn't it work without that?

The mesh in blender:


The mesh in Marmoset Toolbag:


Here the .blend file:
https://www.mediafire.com/folder/b8xga0wnsmwew/blender

In other programs, the same.

Any help is appriciated
Nightfox3
The problem with your mesh are Ngons; Blender can process and show them correctly but once exported you get unexpected results because they are treated in a different way by another program. 

This is what model looks like:



The reason why it worked with Triangulate faces checked is because there were no Ngons any more, all them were converted to tris. You can use this way, however you won't be able to control how it will triangulate faces.

Hence I suggest to start with changed topology of the model (note: it may be a bit complex to redo for all the model, however it will save time further on):