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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:
- 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.
This combination was chosen based on the following assumptions about the
current state of spam on the Internet:
- 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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