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dclug@xxxxxxxxxxxxxxxx wrote: > > Is rDNS just used for email validation or is it used for anything else? The wrapper library can use it to secure services (at least as secure as the DNS is). Useful for stopping the perpetual attempts to abuse services in large companies, where you can say all SSH attempts are only allowed from inside the company plus the admins home PCs. I wouldn't rely on this, but it is sometimes a useful first line to keep out password guessers and such like. Quite a lot of things are compiled with the relevant libraries in. For email servers I configure it so if I have a server "canonicalservername.example.com" with IP address 1.2.3.4 I ensure that the machine greets (HELO/EHLO) with this name, and that the reverse lookup of 1.2.3.4 maps to the fully qualified name of the server. I don't think just the domain is useful in the reverse lookup, as some folk are specifically requiring that the reverse, then forward lookup returns that same IP address. i,e, 1.2.3.4 -> fqdn fqdn -> 1.2.3.4 -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/linux_adm/list-faq.html