I find it difficult to imagine the licensing terms to be reasonable for
most. See:
http://download.microsoft.com/download/6/0/a/60a02573-3c00-4ee1-856b-afa39c020a95/callerid_license.pdf
An alternative with the _same_ feature set can be found as follows:
1) Authenticate and verify the authorization of the EHLO domain with CSV.
2) To restrict the RFC 2822 From domain, list all acceptable EHLO domains
for From domain allowed in a MARID TXT record.
Call the <From:EHLO> (Mailer-ID) and the TXT record the MARID Channel
permissions (MCP).
This would allow authentication to happen without adding a single DNS
lookup. Unlike Sender-ID with DNS timeouts that fail to implement
exponentional back-off while making huge demands upon DNS, or where the
duration of their query may otherwise take hours. By using only names,
the delegation problems are removed. A simple wildcard used in this
permitted list could encompass the required scope. There would not be
CIDR block lists that allows easy abuse.
All the advantages, none of the disadvantages...
-Doug