But currently SPF requires that forwarders install new software for doing SRS.
Well, it's the SRS that requires new software - SPF doesn't require SRS and
therefore doesn't require special software at the forwarder.
Better let those people upgrade the software who have heard about SPF
(those who publish SPF records and those who use SPF records to filter mail)
instead of letting it do by forwarders who might not know what SPF is.
If you whitelist the forwarder at the final recipient, the situation is this:
- The sender does not need new software.
- Forwarders and the final recipient can get immediate benefits of installing
new software that knows about SPF.
- The final recipient has to whitelist the forwarder and cannot use SPF on
e-mails sent via the forwarder, but will probably chose a forwarding service
that has effective spamfilters. The forwarder needs to handle general
spamfiltering like everybody else, and most likely already does it. Most
forwarders are also mailbox providers, and incoming e-mail is processed through
the same spamfilter for both mailboxes and forwarders. There might be a few
exceptions from this, but I think the market will either force these to
implement spamfiltering or put them out of business.
- If a forwarding service cannot deliver to a recipient because of a failed SPF
check, the e-mail will bounce and the sender will know, that the e-mail wasn't
delivered.
Most people don't need SRS. Most people using forwarders don't either - they
just need whitelisting of their forwarder and a forwarder with spamfilter.
Lars.