Deer mark their territory, it kinda smells like horse urine.

Sandy

As silly as it sounds you may be smelling the bushes now that many competing smells are gone. We have yews and at certain times of the year they may smell like soap to a stomach turning scent. Boxwood's are also known for scents.

It probably is one or more things marking their territory but you might want to break off a stem with a leaf and smell each separately.

Boxwood smells (to me) like tomcat spray.

If it is not the bushes themselves, I would suspect cat, since it is near the front door.

That seems to be a favorite place for stray cats to spray. You're lucky they haven't come up onto the front porch and actually sprayed on the door.

Unfortunately, cat spray odor sticks around. Then, of course, as soon as one cat sprays, the rest will come in and spray, and keep repeating.

Don't rule out natural gas. It can have a very different scent after permeating through the soil than it does in the home. Any gas lines nearby?

tj