--On 28 March 2008 12:47:48 +0000 Julian Mehnle <julian@mehnle.net> wrote:
Until no email service provider accepts message submissions outside of their own domains, all email providers offer message submission on port 587, all message submissions are autheticated, and mail forwarders accept responsibility for the email that they forward, it's not safe to bounce email.
This, however, is simply untrue. Of course what you said is desirable, but SPF can help with safely bouncing e-mail _today_.
Only for the minority of domains that publish SPF records. My intention was to convey that SPF will be the solution once adopted.
SPF may sometimes give an unexpected "Fail" result due to alias-style forwarding or other problematic cases, but when it gives a "Pass" result, it is always safe, i.e., the return path can be assumed to be authentic and bounces may be sent.
-- Ian Eiloart IT Services, University of Sussex x3148