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  1. #1
    Join Date
    Jun 2009
    Posts
    83

    Reverse DNS and virtual hosts

    According to an article I've been reading - http://www.crazysquirrel.com/computi...dns-works.jspx - reverse DNS only works if a domain is attached to a dedicated IP address, which can cause problems for virtual hosts with a few different domains pointing on the same IP.

    Short of buying additional IP addresses and dedicating one to each domain on a VPS, what do hosts do about this issue when it comes to things like reverse DNS verification as an anti-spam method? I just find myself scratching my head that mail providers like Yahoo and AOL would use such an inflexible approach (yes, I know Yahoo also uses DKIM, but I have this set up on my own VPS and mail STILL gets refused).

  2. #2
    Join Date
    Mar 2011
    Location
    Dallas, Texas
    Posts
    354
    I don't understand what you mean?

    We allow our clients to set their own RDNS/PTR records for there VM assigned IP Addresses (IPv4/IPv6). It don't cause no problems? Yeah someone's not going to be able to set all there IPs reversed to my.server.com unless they round robin it for it to bounce between all the IP addresses by adding more then one A record I assume,

    But explain more what your talking about, It seems like your stating about how providers offer RDNS control/management to their clients?
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  3. #3
    I think the question is how to deal with RDNS for a server hosting multiple domains. I have seen issues with this on a hosted email provider (just as an example) where the RDNS points to the provider domain, not any of the actual email domain which is used by clients. I think there must be a way to deal with this as large providers who host custom email domains (Google for example) are able to get it done. My guess would be you need to setup the RDNS to point to your hosting company domain, and then somehow register that domain with Yahoo etc. as a valid email provider for reselling domains.

    I would think this is probably going to be a difficult task for a smaller provider. However is anyone is able to workaround this I would sure be interested in how it is possible without giving a dedicated IP per domain. Also would different email domains be a valid reason for different IPs according to ARIN and/or RIPE? It would seem to me if we really want to conserve the remaining IPv4 space having some solution to deal with email would be needed.

  4. #4
    Join Date
    Sep 2004
    Location
    Cluj-Napoca, Romania
    Posts
    462
    You can have a reverse and forward DNS on myserver.mydomain.com and use this IP for SMPTP outgoing to mydomain.com as well as mydomain2.com etc.

  5. #5
    Join Date
    Jun 2009
    Posts
    83
    Quote Originally Posted by ErikD View Post
    I think the question is how to deal with RDNS for a server hosting multiple domains. I have seen issues with this on a hosted email provider (just as an example) where the RDNS points to the provider domain, not any of the actual email domain which is used by clients. I think there must be a way to deal with this as large providers who host custom email domains (Google for example) are able to get it done. My guess would be you need to setup the RDNS to point to your hosting company domain, and then somehow register that domain with Yahoo etc. as a valid email provider for reselling domains.

    I would think this is probably going to be a difficult task for a smaller provider. However is anyone is able to workaround this I would sure be interested in how it is possible without giving a dedicated IP per domain. Also would different email domains be a valid reason for different IPs according to ARIN and/or RIPE? It would seem to me if we really want to conserve the remaining IPv4 space having some solution to deal with email would be needed.
    That's exactly what I was asking. In fact, the last point about the finite number of IPs available was something that occurred to me when I read the article I referenced.

  6. #6
    Join Date
    Jun 2009
    Location
    California
    Posts
    509
    Quote Originally Posted by ErikD View Post
    My guess would be you need to setup the RDNS to point to your hosting company domain, and then somehow register that domain with Yahoo etc. as a valid email provider for reselling domains.
    You're half right. All you need to do is make sure that if your IP resolves to smtp.hostingcompany.com then smtp.hostingcompany.com resolves to the same IP.

    You don't need to register the domain with anybody (unless you're using SPF, and if you are you probably already know what to do), as the sender address does not need to match what the IP address resolves to. To be on the safe side you may want to ensure that the HELO/EHLO name sent is the same.

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