On Wed December 2 2015 23:53:51 Michael Howard wrote:
> I've been getting hammered by spam so tried a few things, rDNS checks
> being one of them. Unfortunately, the mail server checks the rDNS for
> the host (mail.pearsoncomputing.net), the domain alone is not sufficient
> ( See results from 'mxtoolbox.com' - Your Reverse DNS Record (PTR) is
> not a valid host name. According to email sending best practices, a PTR
> Record should be a valid host name. If the PTR Record is not a valid
> hostname, there is a likelihood that you will experience email delivery
> issues with anti-spam services.)

I have been using rDNS checks for as long as I can remember
and I don't see any problems with TDE lists.  TDE list mails
arrive here from 192.119.205.242.  rDNS maps this to
pearsoncomputing.net and DNS in turns maps that back to
192.119.205.242 so no problem.

I think you're running into problems checking HELO
(or EHLO) rather than rDNS.

mail.pearsoncomputing.net is an A record with no PTR
which is allowed but it might be better if it had a
PTR (an IP can have more than one) or if mail.p...
were a CNAME (which is allowed because it is not used
in an MX record or NS record).

One doesn't usually check HELO that stringently but
Tim might want to avoid the problem by setting
"smtp_helo_name = pearsoncomputing.net" in main.cf.

--Mike