... since you have a Mac, why not set up an iCloud email? Doesn't cost anything and I have found it to be highly reliable.
Thanks for the tip; I wasn't aware that I could send mail through iCloud without benefit of my ISP. For the moment, though, I'll stick with my policy of avoiding iCloud.
I was able to contact Russell via MacUpdate, and his response was
you mail server isn't sending a valid SPF. I hardened up my mail server, as I was tired of sifting through countless spam messages each day, to find the real messages. I'll see if I can dial it back a little
That sounds as if he's got some sort of "pref" to allow "suspicious" mail through?
In addition, I've emailed AOL about the problem, which seems to arise on their end, and which, hopefully, they will fix.