Re: [Exim] SMTP+SPF

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Szerző: James P. Roberts
Dátum:  
Címzett: David Saez, Matthew Byng-Maddick
CC: exim-users
Tárgy: Re: [Exim] SMTP+SPF
> > This is
> > also by no means the first time that something like this has been mooted,
> > and every time, it's rejected, mainly because of the enormous amount of

work
> > it requires (both to set up and to maintain).
>
> It took me 10 minutes to publish spf info for about 200 domains. I also
> do not understand your objections to how spf scales. As I know you could
> spf-allow a whole C class with a single line of configuration.
>


I read the SPF proposal, and the first question I had for implementation was,
how to handle classless IP blocks (e.g. /29), other than the painful method of
an entry for each IP. I imagine there is some clever way, similar to how
delegation of such blocks is *supposed* to be done... (*small strangled noises
suppressing off-topic rant*).

Some things I liked about the proposal:

(1) It's optional.
(2) One can publish in advance without
    screwing up anything else.
(3) The onus is entirely on admins for
    implementation, not users.


Some things I did not like about it:

(1) It's optional.  ;)
(2) It is a bit of work to implement.
(3) It's essentially useless until it becomes
    globally implemented.
(4) It stirs up debate about reverse DNS names
    matching HELO/EHLO again.
    (*runs and hides*)
    (Just kidding, Greg!)  ;)


But seriously, the real problem is convincing admins to do the extra work,
long before any actual value is added as a result. Sure, I could publish SPF
data fairly easily; but, I can't *use* SPF data until almost *everyone* does.
It's a bit like asking people to contribute time or money to a "good cause."
You might get a fair number of participants, but you won't get everyone. You
probably won't even get a majority.

I am not objecting to the underlying concept (attempting to validate that
email is coming from a machine it is supposed to be coming from). (Although
SPF is not a particularly secure method, as the paper itself admits). I'm
just saying there are realistic obstacles.

Jim Roberts
Punster Productions, Inc.