Your message dated: Thu, 08 May 1997 15:51:02 PDT

> Now if only something could be done about the a.mx....

    You mean pointing MX RRs at CNAME RRs?

    Unfortunately, although John does a good job of detailing
why listing large numbers of MXes for a domain is bad (see
<ftp://ds.internic.net/internet-drafts/draft-myers-mail-largesite-00.t
xt>),
he doesn't provide any real solutions.  That's because they don't
exist yet, at least, not that will work on the really large scale.

    We're working with Paul Vixie to implement "variadic zones"
(work which we are paying for and which we will contribute back
to the public version of BIND, for the benefit of the entire 'net
community), but until that's been delivered and they are proven to
work, there's just not a whole lot of options there.


    In the meanwhile, more and more sites are depending on pointing
MXes at RRs, because that's the only way they can list a suitably
small set of MXes for their domain (along the recommendations of
draft-myers-mail-largesite-00.txt), while still making use of,
and doing decent load balancing across, their entire set of MXes.
In AOL's case, that's now almost sixty machines.

    Those sites using MXes pointed at CNAMEs should count themselves
lucky.  We came within a hairs breadth of having that option
removed from BIND 8.1, which would have shut down mail to places
like AOL, CompuServe, MCImail, Juno, etc... after they upgraded
their nameservers.

    You're welcome.

--
Brad Knowles                                MIME/PGP: [log in to unmask]
    Senior Unix Administrator              <http://www.his.com/~brad/>
<http://swissnet.ai.mit.edu:11371/pks/lookup?op=get&search=0xE38CCEF1>