How to control reverse DNS lookup through DNS SecurityLicense

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How to control reverse DNS lookup through DNS SecurityLicense

L2 Linker

The user was trying to send a mail from internal to external domain but it is blocking by sinkhole because it is showing as malicious traffic, however, we are able to receive from that malicious domain, Can we block reverse mail from an external server to internal using DNS license. In my case, it has received.


Eg- User mail is and trying to send malicious domain i.e ====blocked by sinkhole policy in NGFW

However, user received mail from malicious domain i.e === can I control using DNS license.


User should not receive an email from any malicious domain so can I control in NGFW using DNS security.


Thanks and Regards,

Cyber Elite
Cyber Elite


DNS really doesn't come into play when you receive an email from an outside email system*. If the IP itself is a known malicious address within any of the PAN lists you could configure a security policy blocking that traffic inbound (and you should), but on a shared/hosted email platform that's not going to be an option.

This is really a job for an email security gateway or a transport rule on your email system. Your firewall can do limited inspection on SMTP traffic and some basic filtering, but you're really going to want to have an actual email security product in place. 


* A lot of email security products and email systems will attempt to resolve the source address if properly configured to figure out if the source is in the SPF or DKIM records. That doesn't mean it's going to resolve back to or anything like that, and that doesn't mean that all systems do that if they aren't configured to do so. 

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