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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: ISP phishing
On Wed, 29 Jun 2005, Tony Finch wrote: > On Wed, 29 Jun 2005, Brad Knowles wrote: > > SPF is not a panacea. > > > > In fact, it is pretty much totally worthless, unless you are the sole > > owner of a given domain and you can guarantee that all mail you ever send will > > always be routed through the machines that you own and control, and you know > > that you don't ever forward e-mail for any of your other accounts. See my other email in regards to this mobile user strawman argument. Look in the archives for the same arguments against closing open relays. > Actually, what you have to guarantee is that you never send email to > anyone who forwards their email elsewhere. This is impossible. This is incorrect. SPF is an inbound filter. This is in the recipients control, not yours. Assume you send email to [email protected] and Alice forwards that email address to [email protected] If the inbound mail server for alumni.miskatonic.edu has SPF or MX+ enabled for [email protected] and and you pass the test and your mail is accepted by alumni.miskatonic.edu then that is the end of your responsibility. If Alice then decides to forward to [email protected] and Alice wishes to use SPF or MX+ for the mailbox [email protected] as well then Alice would whitelist the IP of the outbound mail server for alumni.miskatonic.edu. You don't have control over what forwarding, filtering, or whitelisting Alice does with her personal mailbox. If Alice wants to forward [email protected] to [email protected] and use SPF or MX+ with [email protected] presumably she won't block email from her other account and she can check if she got it right really easy by sending email to [email protected] +----------------- H U R R I C A N E - E L E C T R I C -----------------+ | Mike Leber Direct Internet Connections Voice 510 580 4100 | | Hurricane Electric Web Hosting Colocation Fax 510 580 4151 | | [email protected] http://www.he.net | +-----------------------------------------------------------------------+
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