In <20040114183412(_dot_)GA6875(_at_)dumbo(_dot_)pobox(_dot_)com> Meng Weng
Wong <mengwong(_at_)dumbo(_dot_)pobox(_dot_)com> writes:
So we have the following (possibly conflicting) requirements:
[good list of requirements deleted]
Agreed.
As far as the conflicting requirements goes, the pidgeon-hole
principle pretty much rules out anything that maintains the limits and
doesn't have a database.
Plan A: breaking #2
At pobox, if a user enables SPF filtering, we will do SRS which
respects 1, 3, and 4, but may break 2 if the address is long.
foo(_at_)aol(_dot_)com -> bar(_at_)pobox(_dot_)com -> recipient
we rewrite to something like
bounce+foo#aol(_dot_)com-J0*dG7h8yzAwB=bar#pobox(_dot_)com(_at_)bounce(_dot_)pobox(_dot_)com
-> recipient
Can't you get rid of the "bounce+" part? Also, depending on your
situation, you might be able to get rid of the #pobox.com as long as
it matches bounce.pobox.com. That would save a few characters.
This would be shorter than many VERP schemes that are in wide use today.
Plan B: wildcard DNS
But what if we do this instead?
bounce+J0*dG7h8yzAwB(_at_)foo(_dot_)AT(_dot_)aol(_dot_)com(_dot_)VIA(_dot_)bar(_dot_)pobox(_dot_)com(_dot_)BY(_dot_)bounce(_dot_)pobox(_dot_)com
-> recipient
I can't see any reason why this would be any better than Plan A. It
would also trash the DNS caches across the net.
Plan C: database
If the address is so long that it's not rewritable to one of the above
forms, you fall back to shoving the thing into a database.
Yes. Although if you use plan A, many people will not care enough
about the edge cases to actually follow through with this.
Plan E: shove the original sender into the headers
Pobox will also prepend Old-Return-Path to the headers, showing the
original sender address.
Bounces often don't include much of the original message, you can't
count on getting the headers back. Parsing the bounce message is also
going to be tough.
Forwarders would have to do SRS even if SPF didn't exist.
One point brought up on the postfix mailing list is that without using
SRS, forwarders have no idea if bounces are being created. This is
pretty much the same reason why mailing lists started to use VERP.
-wayne
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