If a company has a lot of old DNS entries for subdomains that point either nowhere (CNAMES that no longer resolve to anywhere) or at servers that are no longer online does that hurt the main domain's reputation for email deliverability or SEO?

I am pushing for a DNS clean up but running up against apathy.

  • Hurt the reputation for what? SEO? Users finding old broken links? – Stephen Ostermiller Oct 3 '19 at 13:07
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    It is at the very least a security leak to keep old sub-domain references out there. Hackers love them! They can be doorways into the internal network infrastructure. If the sub-domains are no longer needed, then definitely remove them. – closetnoc Oct 3 '19 at 15:13
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    The known attack (which should be an even bigger incentive to clean things than the reputation) is if you have records pointing to hosts at shared or cloud providers external to the enterprise. If suddenly those hosts become available (end of campaign, etc.) and someone gets them then it means an attacker has basically control of resources under one of your name. The problem is the same of course if records are still resolving correctly but forgotten which globally more means that you need to keep close track of all external resources you use, specially on shared platforms. – Patrick Mevzek Oct 4 '19 at 4:22

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