On Wed, Sep 15, 2004 at 03:10:51PM -0500, Seth Goodman wrote:
| This gigantic loophole can be closed by using an adjunct protocol along with
| SPF that does end-to-end validation of forwards. SES is one such protocol.
| The combination of SPF + SES gives you what SPF was designed for in the
| first place: confidence in the authenticity of the domain in the
| return-path and immunity from joe-jobs.
I agree that SPF and SES work very well together, and
there's no need to go over the reasons: we've heard them
eloquently argued before.
The only reason I don't think it's advisable to go with an
SES-only recommendation is this:
Because SES depends on a callback verification, it would be
trivial to trigger a DDOS by forging mail from an SES domain
to 100,000 receiving MTAs. Under SPF, those receiving MTAs
launch a bunch of DNS queries. Under SES, those receiving
MTAs start a bunch of SMTP sessions. DNS can support
100,000 queries a lot better than SMTP can.
Therefore the combination of SPF and SES is still needed.