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Reverse DNS lookup on Inbound SMTP

Created: 02 Nov 2007 • Updated: 21 May 2010 | 2 comments
Mailsecurity 5.0.1 on Windows Server 2003 SP1 Stndrd
 
Question concerning the use of Reverse DNS lookup in the software:
 
If this option is checked in the Settings>hosts>localhosts>SMTP>advanced settings page for inbound SMTP what exactly happens to the connection if the sending SMTP server fails rev lookup? The CIO is concerned that some of the smaller clients we work with have misconfigured DNS records which may result in dropped connections and therefore no delivery.
 
Anyone know how SMS 5.0.1 handles reverse DNS lookup failures? I know that it's process intensive and can delay delivery but what else is SMS doing when this is enabled?
 
TIA,
J Penrose MCSE
Net Admin
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Tim Nan's picture
Reverse DNS lookup is not used for connection control.  So even if a server fails reverse DNS lookup and is otherwise considered legit (not on Open Proxy List, Suspect Spammer List, etc.), its message will till be received and processed.