Also, you can convert it to triangles/quads only. Select the mesh (rightclick), enter edit mode (press tab), select all ( press A 'till the whole mesh is orange ), then press Ctrl+T to convert to triangles, or press Alt+J to convert to quads ( doesn't always work, e.g. if you have some faces wrong ).
Press tab again ( back from edit mode to object mode ), then export.
As a sidenote, did you consider OBJ's?