[PLUG] Use "Plus Addressing" for advanced email filtering rules

[TuskenTower <tuskentower@gmail.com>]

I brought up a question about using DNS tricks to handle individual
email addresses so that my cousin and I could assign email addresses
to specific websites (think along the lines of specific use email
addresses).  Take these two for example,
amazon@user1.domain.com
amazon@user2.domain.com
The goal being that both my cousin and I want to use the same name
(because we both have Amazon accounts) for the email address, and keep
our email separate.  Since we control our mail server we could use
aliases, but that is an additional management overhead.  The DNS trick
would make all mail coming in to user1.domain.com sent to user1.

This method forces the sender to identify themselves by the email
address used.  This has the nice benefit, of allowing you to filter on
the receiving address rather than the senders address.  For example, I
used to work for XYZ and I also bank with XYZ.  So I have email from
people at XYZ as well as banking emails from XYZ.  Filter rules would
be much simpler if I could just target XYZ.com, but I can not.  I must
specify all sending emails that correspond to banking with XYZ.com to
separate them from work emails from XYZ.com.

No one was sure of the feasibility of this DNS shenanigan, but  Paul
Snyder mentioned something called "Plus Addressing".  The great boon
that is wikipedia, turned up:
Plus (or Minus) addressing

According to RFC 2821, "the local-part MUST be interpreted and
assigned semantics only by the host specified in the domain part of
the address. In particular, for some hosts the user "smith" is
different from the user "Smith".

Plus addressing is one of the benefits of this limitation. Some mail
servers allow a user to append +tag to their email address
(joeuser+tag@example.com). The text of tag can be used to apply
filtering.

Some systems violate RFC 2822, and the recommendations in RFC 3696, by
refusing to send mail addressed to a user on another system merely
because the local-part of the address contains the plus sign (+).
Users of these systems cannot use plus addressing.

On the other hand, most qmail installations support the use of '-' as
a separator between local-address and domain parts. Such as
joeuser-tag@example.com or joeuser-tag-sub-anything-else@example.com.
This allows qmail through .qmail-default or
.qmail-tag-sub-anything-else files to sort, filter, forward, or run
application based on the tagging system established. Procmail and
SpamAssassin are common applications to use with qmail to help sort
out spam or further filter incoming email.

http://en.wikipedia.org/wiki/E-mail_address#Plus_.28or_Minus.29_addressing

HTH
Amul

PS yes I am just a little looney, and I have a pay for play contract.
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