Yes, You can appear for IIT JAm provided You Meet the other eligibility Criterion. As IGNOU is recognized University and IIT JAM does not mention that they would Not accept correspondence course.

The eligibility criterion for JAM: All candidates admitted through JAM should have a Bachelor's degree. and You should have 55% or 5.5 CGPA in Bachelor degree for Gen OBC and 50% or 5.0 for others.