First of all, have you taken your cat to the Vet's to make sure he doesn't have any infections of any kind? Example: urinary tract infections, etc?
If your cat has been checked by your vet and doesn't have any infections, he could be "marking his territory" outside.
Is there anything new in your lifestyle that he may not be favouring? He might be trying to get your attention by being naughty. If so, you might try and make him know that he's still part of the household by giving him extra attention, etc.
Inside your home, cats are very clean and will do anything not to soil your belongings. You may want to invest in another couple of kitty litter pans and put them wherever your cat is lifting his tail in your house. Keeping the kitty litter pans clean at least twice a day will also help.
There are spays on the market which are quite effective that will discourage your cat from spraying.
© Nancy Kitching 2002
Dog Trainer Member of CAPPT, CKC, OKC (Ottawa Kennel Club),
and Bytown Obedience Club in Ottawa.
Hudson, Quebec J0P 1H0