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  • rdns / smtp

    Hi there,

    I hope someone can help me.
    Untill recently I used to have a linux mailserver. I wanted to try and switch to a Windows server and with the help of the articles on Petri I created a Windows 2003 server with Exchange 2003. Both have all the SP's and are configured with SSL OWA / RPC over HTTP.
    It's a single server inside a small domain behind an ADSL. Internally I have a local DNS and I have a domainname registered with all the DNS entries pointing to my modem/firewall.

    After changing to Exchange, I couldn't send to hotmail addresses for the well-known "local #5.5.0 smtp;550 DY-001 Mail rejected by Windows Live Hotmail for policy reasons. We generally do not accept email from dynamic IP's as they are not typically used to deliver unauthenticated SMTP e-mail to an Internet mail server. "
    My IP is also listed in the PBL of spamhaus. Searching on spamhaus told me I should have smtp authentication turned on and a reverse dns present.

    I called my ISP and they told me they didn't support RDNS. They "only provide the line"....
    The strangest thing though: while hosting on the linux server, I didn't have any problems with sending to hotmail without a rdns entry.

    So, my question is: is there a way to have exchange increase the smtp authentication / security in a way that the rdns entry isn't needed???

    I'm looking for ways to change ISP..


  • #2
    Re: rdns / smtp

    First line support usually don't know what Reverse DNS is. It is also known as PTR records.
    Do you have a static IP address? If you do then you should be able to get a reverse DNS set. Ask for the call to be escalated past first line support to someone with a clue.

    Did the spamhaus search actually say why you were listed? It could be an open relay, or that you are in a dynamic IP address block. If you only have a single IP address then it could be because a machine on your network has been compromised.

    With Exchange, you also need to set the SMTP banner correctly.
    ESM, Servers, <your server>, Protocols, SMTP. Right click on the Default SMTP VS and choose properties. Click on Delivery and then Advanced. Change the FQDN to match what your server is known as on the internet - for example.

    Simon Butler
    Exchange MVP

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