OT (again): SA-SPF opinion

[Mike Brudenell]

Greetings -

--On 26 May 2005 16:54:06 -0400 Stephen Swaney <steve.swaney at FSL.COM> wrote:

> I believe that SRS, Sender Rewriting Scheme, is only required if you are
> relaying form you SPF hub. A typical example would be an ISP who is
> relaying email from a home pc or a business hub that sends their outbound
> email through the ISP's "smart relay". The ISP in this case has to
> rewrite the header to make it look like the mail was sent From the smart
> relay.

It is also needed if, as a courtesy, your organisation allows current or 
past members to forward their mail off-site to an alternative mailbox. 
Here at our University we:

  * ...currently permit people to forward their incoming mail to an off-site
    address (although I understand this is currently under review) --
    perhaps they're currently on sabbatical at another institution.

  * ...permit students and members of staff who have left to forward
    their incoming e-mail on to a new address for a period.  For example
    this helps graduating students receive replies to requests for job
    information that they have sent out.

In these common setups you are effectively relaying incoming mail arriving 
from an off-site source to a different off-site destination (albeit not in 
an 'open relay' manner!).

We know from experience that without SRS this can cause problems if (a) the 
source publishes an SPF record and (b) the destination validates this.

This implies that even if you choose not to publish an SPF record yourself 
you can still be put under pressure to implement SRS if you operate any 
such forwarding policy.

Cheers,

Mike Brudenell

-- 
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