Hello
Unfortunatly, Ferret's do have a distinctive smell. You may have reduced this slightly by having him neutered. However, if he gets frightened he will let off a scent to warn any preditors away.
The comment above is good - make sure the litter tray is cleaned out regularly to reduce odors, make sure the bedding is natural - we use hay inside a carboard box when they live inside, and hay in a wooden hutch when outside.
Hope this helps.
Hi
I would ask your pet supplier if they have anything that will help. Also you don't say how long you've had him? IF he is quite new then he will be a bit stressed which can make them smell more.
Also check what you're using for bedding, some substrates hold more smell than others. I use sawdust in the pull out tray (to easily catch any wee wees, also make sure you got every little bit) and they have fabric bedding everywhere else which can be easily washed once a week with some bicarb of soda.
I clean mine out twice a day and use baby wipes to clean all the surfaces inside Ferret Mansion, this helps A LOT. Unfortunately, they're just stinky lil critters really.
Hope this helps?