On Mon, 4 Apr 2005, David MacQuigg wrote:
I really like the way CSV avoids all the complexity in SPF. I'm puzzled,
however, as to why you chose SRV records instead of a free-format TXT. As I
understand it, this limits you to authorizing just one or a few servers.
CSV is concerned with the HELO domain not the mail domain. There can be
any number of HELO domains for a mail domain, i.e. any number of mail
servers - there's usually a one-to-one correspondence between HELO domains
and mail servers. For example the mail servers for the mail domain
cam.ac.uk (and most of its subdomains) are called ppsw-N.csi.cam.ac.uk
for various values of N, and each of these would have CSA SRV records
entirely independently of the domain cam.ac.uk.
SRV records provide an optimisation, since a single DNS lookup provides
both the authorization details and the IP addresses of any authorized
host(s).
Tony.
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