On Wed, Jun 29, 2005 at 04:30:59PM -0400, John Hinton wrote:
| Jamie Cameron, the person behind Webmin, is adding some functions to the
| interface to add/edit SPF records to the Bind module and the Virtualmin
| module. He has asked me to summarize the differences between +,-,~ and
| ?.
A few months ago, Mark Lentczner mentioned that if we had
the chance to do SPF over, it might be wise to define only
the positive mechanisms (a, mx, ip4, etc) and not address
the question of prefixing "all".
That way, a record would look like
"v=spf1 a mx ip4:192.0.2.0/24"
and there would be no "?all" or "-all" or "~all" at the end.
Reason being: the transition from ?all to -all is something
that happens at the widest possible scope, at the global
community level. Receivers are going to take the SPF input
under advisement and still do whatever they think is best
anyway.
So the small utility offered by a sender distinguishing
between ? and ~ and - is probably exceeded by the trouble of
explaining and justifying and arguing over the differences.