The blocking of your e-mail appears to be caused by invalid rDNS mapping. Here's a graphic of the test results from
the Mail Server Test Center at www.dnsstuff.com
. Note that this site requires a free account before you can login and run further tests.
If you run your own SmarterMail server, then you will need to contact your co-location company or, if you have your servers in a facility under your control, the company who provides your internet connection, to have the FQDN (fully qualified domain name) or your mail server REVERSE mapped to the PUBLIC, STATIC, IP address which it uses to send and receive e-mail.
Those mappings will use the following information:
188.8.131.52, to mxin.name-services.com, and;
Once this reverse DNS mapping has been properly mapped the rDNS tests will no longer fail and your mail should, once again, be accepted. Once the rDNS has been properly configured, the red word MISMATCH, shown in the test above, will turn black and say MATCH
If you do not operate your own mail server, then you should contact your hosting company and forward this information to them.
Phonr: (773) 491-9019
Phone: (224) 444-0169
E-Mail and DNS Security Specialist
Network Security Specialist
Customer Service Portal: https://portal.chicagonettech.com
Security Blog: http://networkbastion.blogspot.com/
Web and E-Mail Hosting, E-Mail Security and Consulting