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|  | Tagged Message Delivery Agent (TMDA) |  TMDA is an 
open source software application designed to significantly
reduce the amount of 
spam
(Internet junk-mail) you receive.  TMDA strives to be more effective, 
yet less time-consuming than traditional spam filters. 
TMDA can also be used as a general purpose 
local mail delivery agent 
to filter, sort, deliver and dispose of incoming mail.
 
 The technical countermeasures used by TMDA to thwart spam include:
 
This combination was chosen based on the following assumptions about the
current state of spam on the Internet:whitelists: accept mail from known, trusted senders.
 
blacklists: refuse mail from undesired senders.
 
challenge/response: 
allows unknown senders which
aren't on the whitelist or blacklist the chance to confirm that their message 
is legitimate (non-spam).
 
tagged addresses: 
special-purpose e-mail addresses such as time-dependent addresses, or
addresses which only accept certain kinds of communication.  These
increase the transparency of TMDA for unknown senders by allowing them
to safely circumvent the challenge/response system.
 
 
You cannot keep your email address secret from spammers.
 
Content-based filters can't distinguish spam from legitimate mail with sufficient accuracy.
 
To maintain economies of scale, bulk-mailing is generally:
    An impersonal process where the recipient is not distinguished.
A one-way communication channel (from spammer to victim).
 
spam will not cease until it becomes prohibitively expensive for spammers to operate.
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