acceptable trees for mulch

in general what kinds of trees should i not use as mulch.

It would help if  you added your general location.
If you're in the U.S., I think black walnut's a no-no.
We use everything over here.

Not cedar and not walnut. Both of those trees have a chemical in them to suppress wee growth, and what are weeds but plants? We had walnut trees when I was growing up and my Mom had to place the garden outside of the root growth of the trees or the vegetables would  not grow well.

I mulch up maple saplings, or use them for natural building. A strong young wood.