Andrew Norris wrote:
Back to the PTR RR:
$ dig +short MX bobhoffman.com 10 mail.bobhoffman.com. ^^^^^^^^^^^^^^^^^^^^ $ dig +short A mail.bobhoffman.com 72.35.68.59 $ dig +short -x 72.35.68.59 bobhoffman.com. ^^^^^^^^^^^^^^^
mail.bobhoffman.com != bobhoffman.com
so what? mail.bobhoffman.com is the MX. bobhoffman.com is an RMX.
$ host -t mx yahoo.com yahoo.com mail is handled by 1 e.mx.mail.yahoo.com. yahoo.com mail is handled by 1 f.mx.mail.yahoo.com. yahoo.com mail is handled by 1 g.mx.mail.yahoo.com. yahoo.com mail is handled by 1 a.mx.mail.yahoo.com. yahoo.com mail is handled by 1 b.mx.mail.yahoo.com. yahoo.com mail is handled by 1 c.mx.mail.yahoo.com. yahoo.com mail is handled by 1 d.mx.mail.yahoo.com.
no one of these is web23004.mail.ird.yahoo.com, ...
This may not be your main problem, but it certainly isn't helping matters.
If we ignore the surrounding IPs (too many without rDNS), he has a very simple setup, that should not cause any problems.
Yahoo seems to be pretty picky on reverse DNS. I had a VPS running a mail server where the PTR matched the host. I was relegated to yahoo's spam folder until changed from the default PTR which looked mildly like a dialup.
generic PTRs are a different matter.