spf-discuss
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[spf-discuss] Re: Need some help understanding this situation

2007-06-13 00:58:16
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Per Jessen wrote:
we are an email filtering service so we "sit" in between our customer
and people that want to send them email.  (we obviously use MX
redirection).

We have a situation where "adjoli.de" wants to send a perfectly legit
newsletter to my customer, but is being rejected by the customer
mail-server due to our servers not being listed by the SPF record
for "adjoli.de":

"v=spf1 ip4:194.29.239.0/28 ?all"

The customers mailserver is smart hosted by a provider, nothing unusual
about it.  The question is - is it _right_ to plainly reject the email
from "adjoli.de" when the spf evaluation says "Neutral" ?

Two solutions:

 A. Either you rewrite the envelope sender for all mail you forward to them
    to a different domain -- one that belongs to _you_.  E.g.: you receive
    a message with MAIL FROM:<user(_at_)adjoli(_dot_)de> for your customer.  
When you
    forward it to your customer, instead of repeating the MAIL FROM:<user@
    adjoli.de>, you say something like MAIL 
FROM:<user+adjoli(_dot_)de(_at_)spamchek(_dot_)
    ch>.  (In fact, this is a bit more complicated if you want it to be
    secure -- see SRS AKA Sender Rewriting Scheme[1,2].)

 B. Or your customer exempts mail forwarded to them by you from their SPF
    checks.  If they choose to do that, it would be good if _you_ then did
    the SPF checks for them (don't know whether you already do).

References:
 1. http://www.openspf.org/SRS
 2. http://www.libsrs2.org/srs/srs.pdf

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