Trend Micro Email
                  Security adds a layer of protection by validating the
               reverse DNS (rDNS) records for inbound email messages.
With the reverse DNS validation feature, an administrator can configure the following:
               
- 
Validation settings: whether to reject an email message when the corresponding PTR record is missing or invalid
 - 
Block list: a list of PTR domains for message blocking
 
During the SMTP connection setup stage, Trend Micro Email
                  Security uses the
               email sending IP address to perform rDNS lookup. If the query result matches the criteria
               in any
               rDNS validation settings or the PTR domain block list, Trend Micro Email
                  Security rejects the email message before the message body is
               sent over.
NoteIf the IP address sending an email message matches the Approved IP address list of
                              IP
                              reputation, the email message bypasses revere DNS validation. 
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