So you want to sign up for a forum or something but don't want them spamming you, ie you don't need 5 emails perday on irrelevent crap such as DrPatPong has lost his cat or other such rubbish.
First stop is getonemail.com or any of the other similar sites, generate your one time use email addy, you can see it in the first picture under section number 1.
Go to the website or forum or whatever it is that you want to join, fill out the registration details, paste in your one time use email addy, click register, now go back to getonemail.com, check for mail and click your registration confirmation link, and thats it, your a member and will never be spammed by them, everything will bounce back on their server and help up their spam score, ie all the shite they would normally try to spam you with.