Quoting Lyle Schofield (Lyle(_dot_)Schofield(_at_)daou(_dot_)com):
I'm surprised that AOL is blocking this way. I knew that a lot of major
ISPs were jumping on the bandwagon, but I didn't realize SPF had the
kind of penetration that would allow you to only accept Email based on
AOL is not (yet) blocking based on SPF alone, although it is one of the
criteria they use. I spoke to someone at the office of the postmaster at
AOL. The domain whitelisting is much more important in getting mail through
to AOL than SPF is at this moment, although that will change. As was said,
though, SPF is easy enough to implement espescially if you control your own
dns so you might as well get it done.
AOL's 'postmaster' support people are surprisingly helpful and cooperative,
and actually follow up to make sure things work. Maybe that shouldn't be
surprising, but it wasn't my expectation prior to calling them. I've now
dealt with them 4 or 5 different times on various issues, and found them
to be among the best ISP support people I've dealt with.