Chris Kovacs replies: Spanish Cedar is an excellent substitute for mahogany in outdoor millwork. Spanish cedar is quite soft however and does have a fairly noxious odor when milling. A much heavier and harder substitute would be utile (Entandrophragma utile) which is imported from Africa. I have used it for several exterior doors and millwork and it paints well and holds up well. Utile’s main drawback is its weight and hardness which can cause saw blades, jointer and planer knives to dull quickly.