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add &quot;HACK(`require_rdns')&quot; without quotes to your sendmail.mc file the m4 it....this will make sendmail check for rdns records and reject the senders if it dosn't match their A record and MX record.
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add "HACK(`require_rdns')" without quotes to your sendmail.mc file the m4 it....this will make sendmail check for rdns records and reject the senders if it dosn't match their A record and MX record.

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I am looking for details of how to update the sendmail.cf and sendmail.mc so that Sendmail will refuse to accept inbound mail from any smtp host that does not have a resolvable reverse DNS entry. &nbsp;I found some code that may do it, but it does not seem to work -- maybe it's in the wrong location. &nbsp;Any help would be most appreciated.<br />

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I am looking for details of how to update the sendmail.cf and sendmail.mc so that Sendmail will refuse to accept inbound mail from any smtp host that does not have a resolvable reverse DNS entry.  I found some code that may do it, but it does not seem to work -- maybe it's in the wrong location.  Any help would be most appreciated.


Sendmail: how to reject SMTP connections that are not DNS reverse mapped?

Networking is the process of connecting computing devices, peripherals and terminals together through a system that uses wiring, cabling or radio waves that enable their users to communicate, share information and interact over distances. Often associated are issues regarding operating systems, hardware and equipment, cloud and virtual networking, protocols, architecture, storage and management.

Networking

The Domain Name System (DNS) is a hierarchical, globally distributed system responsible for associating the name of a computer, service or other resource into an IP address for connecting to the Internet or a private network. Most prominently, it translates domain names to the numerical IP addresses needed for the purpose of computer services and devices worldwide.