Why not just do it?

Ed Crowley MCSE+Internet MVP
Freelance E-Mail Philosopher
Protecting the world from PSTs and Bricked Backups!T

-------------------

I am still learning about.  I read this on this FAQ about breaking e-mail
forwarding http://spf.pobox.com/faq.html.    Do you recommend everyone set
this up?


Does SPF break email forwarding?

Yes, it does. You'll have to switch from forwarding, where the envelope
sender is preserved, to remailing, where the envelope sender is changed. But
don't worry, we're working on providing SRS patches for the four major
opensource MTAs, so that when you upgrade to an SPF-aware version, this
problem will be solved also.

If your forwarding runs through a commercial service like pobox.com, you
shouldn't have to do anything. They have to change with the times, and
perform the above rewriting automatically for you. SRS is a structured
standard that helps them adapt.

Until the SRS patches are ready, the following workarounds will preserve the
important functionality.

Suppose you have a .forward file that says [EMAIL PROTECTED]  
If your system uses Procmail, you can replace the .forward with a
.procmailrc that says: 

    :0
    * !^FROM_DAEMON
    ! [EMAIL PROTECTED] !^FROM_DAEMON is just a safety check --- if the
[EMAIL PROTECTED] address bounces, the bounce won't cause a loop.  If you don't
have procmail, the .forward could instead just say "|/usr/sbin/sendmail -oi
-f [EMAIL PROTECTED] [EMAIL PROTECTED]"

This would make sure the sender address on bounces is "nobody", so if that
bounce bounces, it would be junked. The address
"[EMAIL PROTECTED]" should of course exist and be mapped to the
bit bucket.
 
The most advanced solution is to forward bounces unless they contain the
X-Loop token or the forwarding address. This is better than the first form,
which deletes all bounces, whether or not they'd cause a loop.

    # loop protection
    :0 fw
    * !^X-Loop: [EMAIL PROTECTED]
    | /usr/bin/formail -A'X-Loop: [EMAIL PROTECTED]'

    :0 A
    {
        :0
        * !^FROM_DAEMON
        ! [EMAIL PROTECTED]

        :0 B
        * [EMAIL PROTECTED]
        ! [EMAIL PROTECTED]
    }This can even be combined with the above "-f nobody" solution, although
if the forwarding bounced once, there usually isn't much point in trying to
forward the resulting bounce again, so delivering locally (at the forwarding
site) would then be better... but that assumes that this is possible.
 

You can't make an omelet without breaking eggs, and unfortunately forwarding
is the egg that breaks. We're doing our best to patch it back together with
SRS.

What if I don't control my DNS records?

More and more DNS service providers are supporting TXT records. You can find
a list of them at http://www.telefonica.net/web/news/spf/. If yours is not
on the list, write to them and ask for TXT support!


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