The SANS ISC Handler Diary is asking for your experiences with SPF. Its funny timing because i just configured SPF for my domains last night. I’d been using SPF records previously, but when I left PowWeb for Dreamhost (which changed my authoritative DNS server) I didn’t set up SPF again.
I’m using Google as the mail server for my personal domains. Configuring SPF for google is pretty easy. Just create a txt record for v=spf1 include:_spf.google.com ~all. Like most SPF implementations, they recommend you use “~all” which tells the remote server the list of authoritative servers is merely information and not to reject mail based on this alone. I kind of wonder what use that is. But it seems to take more guts to use a “-all”.
To me, SPF is not exceptionally useful. It just seems like the only thing you can do to prevent yourself from being Joe Jobbed. Sadly through the years remote mail servers are more likely to allow backscatter than use SPF.
At the same time, its never shot me in the foot. ~all instead of -all is probably to thank. I have seen Hotmail headers that indicated that if I was using -all they would have blocked me. They just had a screwed up implementation that couldn’t handle “include” statements in SPF records. SPF is not well liked by *nix folk. It breaks .forward. It breakes mailing lists that send as the message poster.