If they do not want to receive it, then typing some spurious addy, like a@b.com, will satisfy most simplistic checks. I don't know which poor blighter has the email addy a@b.com, but they must recieve a sh^H^H lot of junk they never asked for.

I get spam at no@tnx.nl, which doesn't exist. But I get more spam even at aoeu%aoeu.nl^s/%/@/, which does exist. I feel sorry for the person who has asdf@asdf.com.