Sorry for the confusion. I should have said - How about allowing one range
of IP addresses? That range could be specified using CIDR notation.
We all know what a CIDR block is. That's not the question.
This is the question:
If you are trying to address another issue with your CIDR suggestion, is
there any reason that a single host's HELO would need to be associated
with multiple A records other than (1) multi-homing or (2) using a domain
name rather than a host name for a HELO?
If a host name is multihomed, it should be obvious that the addresses
are in address ranges that are routed differently.
Think of some overworked guy who spends all day answering help desk calls
at a small ISP. One day he has to deal with a new problem - some
"authentication thingy" that is causing his outgoing mail to be rejected.
The small ISPs I know have maybe three mail hosts. After he spends 20
minutes researching what the heck CSV is, don't you think it would be
better for us to encourage him to to spend 3 minutes adding his three
correct CSV records rather than 2 minutes adding a bogus CSV record
with a bogus overbroad CIDR block that would doubtless include all of
the spam zombies in his DSL range?
One last comment on syntax and record complexity: Think what will happen
if we ever have a consolidated DNS record including domain ratings, data
from other authentication methods, etc. CSV could have a significant
advantage over other authentication methods.
One of the few good things that happened in MARID is that MS' proposal
for a bloated omnibus DNS record was thoroughly discredited.
R's,
John