Mailing List Message #7591
From: Avi Rappoport <>
Subject: Re: Whitehole Entries
Date: Fri, 26 Jan 2001 14:19:33 -0800
To: SIMS Discussions <>
Everyone should take a look at XNS <> and OneName <>.  This is an initiative to have positive identification of email senders so you can trust them.  Adam Engst of TidBITS is involved, which gives it a lot of credibility in my eyes.


At 4:06 PM -0500 1/26/01, Bill Cole wrote:
At 2:28 PM -0400 1/26/01, Paul Galati wrote:

Am I supposed to tell my users that they now have two addresses; 1
for nice mail servers and 1 for open relays.  Tell them to use the
nice mail first.  If it does not work and get's caught by maps, then
use the other address.  That is silly.  Is that typical for ISP's to
do that?

Tagged addresses are a very common feature. They are built into sendmail, the most commonly used MTA.  It's not a matter of having 2 addresses, each user has an extremely large number of possible addresses that they can invent on the fly which all automatically deliver to the same mailbox. The tags do with some reliability what cannot be done by a sender address: they identify the sender with some certainty.

It is not at all uncommon for end users to work out something along the same lines: a 'real' address that they only give out to people they know and one or more other addresses that they give out more freely. Hotmail owes a lot of its scale to this sort of tactic. The nice thing for users about tagged addresses is that they all go to the same place and a user can create a new one at will without any setup. They also make client-side filtering easier, becaue mail sent to a tagged address will have that tagged address somewhere in it, and that is a good identifier of where it came from. For example, most of the mailing lists I subscribe to  are subscribed with some sort of tagged address specific to that one list, so even when they change the details of how a list is run (i.e. server moves, sender changes, etc.) my Eudora filters still can identify the incoming mail as being from a specific list (or perhaps from someone who got the address from that list.)

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