Brian Keefer wrote:
The other options is to stuff all the spam messages in a folder and expose them to the user, taking up a huge amount of storage space for something the vast majority of users are never going to look at any way.
Which is, in fact, what Yahoo! does by default. Users have the option to have that stuff deleted immediately, should they desire.
Blocking an entire site just because one John Doe user clicked a button they don't even understand just does not make sense.
You're right -- but Yahoo! has a sufficiently large userbase that they can count multiple complaints before blocking anything. Same story with AOL, and Hotmail, and Cloudmark, and many others who've used this technique for years. In all of those cases, they have safeguards to prevent gaming, to prevent bouncing, and pretty much everything else anyone's suggested thus far in this thread.
Last, anywhere that I've seen extensive use of forwards has had a maze of difficult to untangle abuse problems related to forwarded spam. Any site allowing forwarding should apply very robust filtering of outbound mail.
Very true. MAAWG published a document last year which includes some additional recommendations: http://www.maawg.org/about/publishedDocuments/MAAWG_Email_Forwarding_BP.pdf -- J.D. Falk Return Path Inc http://www.returnpath.net/