Great Circle Associates List-Managers
(March 1996)

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Subject: Re: Majordomo and virtual domains.....
From: "Jason A. Dour aka Dark Father Amadeus" <jadour01 @ homer . louisville . edu>
Date: Sat, 23 Mar 1996 12:47:14 -0500 (EST)
To: list-managers @ greatcircle . com
In-reply-to: <v02130512ad75ede959f1@[]>


On Wed, 20 Mar 1996, Brent Chapman wrote:
> It's part of a series of hacks to my file that I've developed
> over the years; let me see if I can isolate just those changes.  No
> guarantees; you'll have to play with this in your own environment to get it
> to work.

Hello all,

        I am pleased to see this topic arise.  I am presently about to
move four or five mailing lists (currently run through Mdomo) to a machine
that will be servicing at least two domains and several machine names...

        Recently, I've been doing some consulting for a firm...a portion of
which involved setting up email services for a company, as well as another
company who is "riding the coattails" of the other.  The primary company
owns the machine, and it responds primarily to their domain.  The secondary
company is to be a virtual domain.

        Obviously, since both companies wanted various standard email
addresses (webmaster, postmaster, etc.), I had to implement virtual mail
hosting.  I did not, however, want to do a class replacement that then
relied on the aliases file -- as Brent has suggested -- and here is why...
*outgoing* email needed to reverse resolve the same addresses.

        For example: is the service account for the
secondary company.  When someone sent email to, it
should go to  Easy enough with class replacements
and aliases, but it only works one way...

        How to get the outgoing email to be rewritten?  DBM lookups in
ruleset 1 for sendmail.  To use the same method for incoming mail, use DBM
lookups in ruleset 2 for sendmail.  That way, when someone sends mail to, it goes to  And if replies, then it is sent as the original address:

        I've implemented this routine for the my customers, and they are
quite pleased with the results.  Obviously, support scripts to maintain the
DBM lookup tables also had to be written.  Obviously, this involves having
two levels of aliasing available: forward only with the aliases file, and
forward and reverse with the DBM lookup tables.

        My question for Brent (and everyone else as well), is this: does
this present major problems when using some listserving software (in this
case, Mdomo)?  Theoretically, I could have a forward lookup table that
resolved: -> "wrapper...  blah blah blah" -> "wrapper resend ... blah blah blah"

And then when Mdomo resent the mail, the outgoing lookups would be resolved
as:  -> ->

This way, you get both incoming and outgoing handled at the MTA level, with
less tweaking at the Mdomo level...theoretically.

I've found that forward DBM lookups are common (especially with ISPs), but
reverses are not (at least the information was not readily available on the
net that I could find)...why?  Has anyone implemented something similar to
the above in practice?  If so, does it work successfully?  What is the
scalability of such a system like for heavily loaded machines?  Is it
possible to simply hack the aliases file to allow "@" in the LHS?  Is it
possible to use the DBM lookups *only* when necessary (perhaps with a class

These are all issues (and there are probably more) to using such a system.
It just seems easier to me on the administration end.  Any comments,
suggestions, et cetera?
+ Jason A. Dour  a.k.a.  Dark Father Amadeus         Finger for Geek Code, +
|                      general info, and     |
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