On 16/07/2016 11:35, Jim Reid wrote:
That wouldn’t have worked anyway.
Assuming a reverse lookup of an IP address returns a name -- a big if
-- there’s no guarantee that name has any relation to whatever domain
name is in the MAIL FROM.
For instance, lots of organisations outsource their email to
specialised hosting/service providers. A MAIL FROM might well say
example.com while the reverse lookup returns some name in
$emailprovider.com for a server that’s delivering email sent by
bazillions of customers.
No guarantees of course but the majority of valid MX servers return a
name.
It would have worked for smaller orgs where they usually have one MX
server and a relativly simple mail and domain setup. Besides, this would
have been a white listing only method so no harm done other than the
additional DNS lookups but I guess it is not postscreen's job for this.
