[ExI] Avoiding Spam

[Ben Zaiboc]

Can anyone tell me what's wrong with this plan (I'm assuming something 
must be wrong with it, because it's such a simple idea, but I've never 
heard of it being used)?

For every email account you have, you get a 'dark' twin account, the 
address of which is never published (something like 
"bensemaildark at bensdomain.etc", paired with "bensemail at bensdomain.etc". 
In fact, you don't even need to know it yourself).  This means that 
nobody will ever send an email to that address - except for spammers.  
Incoming mail to both accounts is hashed, the hashes compared between 
the two accounts, and any matches indicate spam, which can be deleted 
from the 'real' account on the server, before it even gets to your local 
inbox.

The only downside I can see is the extra processing needed on the mail 
server.  If that seems likely to be a problem, it could be implemented 
locally, and the overhead is yours, not the providers. Spam would get 
downloaded, then immediately deleted, so at least you wouldn't see it.

There might be a problem with the hash function, if spam varies 
according to the email address it goes to, but even if this is a thing, 
it's not unsurmountabe.

Any thoughts?

Ben