IF you try to send email out to certain party and you get bounce error message stated :-
450-4.7.1 Client host rejected: cannot find your reverse hostname
Explaination
The error message displayed in the bounce back “Client host rejected: cannot find your reverse hostname, indicates that the IP from where the email originated does not have the appropriate PTR record. This email was rejected by the recipient AntiSpam server. They require remote servers sending emails to their anti-spam servers to have proper, fully compliant reverse DNS (also referred to as fcRDNS on the Internet). Please see http://www.dnsstuff.com/reverse-dns-faq/ . This helps them to detect trojaned PCs trying to send them spam and/or viruses.
IF sender use another hosting provider service, they need to contact their provider and ask them to add an appropriate PTR record for their server ip. IF they use their own mail server, ask their line ISP/line provider which provide the fix ip and request to add PTR record for their ip. The PTR record should be added at the ISP level.One matching pair of PTR and A records is sufficient, so even if have multiple A records pointing to the same IP address, having any one of them in reverse DNS is sufficient. Note that this does not exempt the sending host from other anti-spam checks.
To illustrate:
$host qmail-a.directi.com
qmail-a.directi.com has address 66.98.146.35
$host 66.98.146.35
35.146.98.66.in-addr.arpa domain name pointer qmail-a.directi.com.
$host cbl.abuseat.org
cbl.abuseat.org has address 216.168.28.50
$host 216.168.28.50
50.28.168.216.in-addr.arpa domain name pointer cbl.abuseat.org.
You can check whether your email server ip has PTR/Reverse DNS/Reverse Hostname or not through this website
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