If you want a deeper clean for your external door, then you might want to consider using paint thinner for the areas where dirt and grime have built up.
Using a soft cloth, apply a few drops of paint thinner to it and gently rub the grain of the wood in circular motions. Once all the dirt has been removed, it’s important to wipe over the area with warm soapy water to ensure that chemicals aren’t left on the wood.
Once dried, use a furniture polish over the top to protect the treated wood.