Hi,
By publishing SPF you are declaring that you want to change
the way the
world works, even though this particular change doesn't seem
necessary.
By issuing a 551 response to mail from you when you've
published an SPF
record, the forwarder can continue to operate as normal for
most people,
while still giving _you_ the address to which mail is being forwarded
today. If you want to send your mail there directly, you can.
The optimum solution:
Forwarders don't, they simple tell the sender what address to use, the
sending MTA then uses the new address. If it cannot send, it can bounce to
the author with a sensible message:
Mail from: me
Rcpt to: c(_at_)d
551 - Would forward try <a(_at_)b>
...
Mail from: me
Rctp to: a(_at_)b
550 mailbox xxxxxx
....
Message failed. Address a(_at_)b (redirected from c(_at_)d) failed due to
mailbox
xxxxx
Forwarders don't even have to transfer the mail, they just have to tell the
orinal MTA where to send the message. Authors can tell receipients (if they
care) why mail is not getting through. (I for one hate getting a bounce for
an address for which I have no clue of why the message was going there.)
It would take time for this to filter through the net and during that time
we may get bad bounces etc. but that was the case with open relays and that
situation is getting close to being closed.
The ideal solution is for one hop delivery. My MTA to your MTA with no one
in the middle. To achieve that we need MTA's to act on "No longer here, try
here" replies. The .foward files can be usd to supply this info.
Then SPF will work for all, Christmas will come early, we all get a bonus
and there will be world peace (well maybe one day) :).
Richard.