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Thread: Reverse DNS / SMTP trouble

  1. #1
    Junior Member
    Join Date
    Jun 2003

    Reverse DNS / SMTP trouble

    Hi everybody - I have a question for the DNS and SMTP experts...

    Unfortunately if I want your help on this matter I can't really keep much info private.

    I am (trying to) run a mail server for a domain which I purchased ( I also have
    registered a free one ( They point to the same IP address and my mail
    server will accept messages for either domain. That IP address is dynamic and I know this
    complicates things, but set that aside for the moment. Suppose I try to deliver a message
    to/through another MTA from my ideal email address (

    451 4.1.8 Domain of sender address does not resolve

    OK - A number of servers give me an identical error when I attempt to use
    as the source address. Now, using a hotmail account or something I try to use
    as the destination address:

    451 Name server timeout
    Message could not be delivered for 5 days
    Message will be deleted from queue

    That is obviously from one particular server but others produce a similar effect - undeliverable
    and returned mail. My first guess concerned reverse DNS. Everyone says this is the responsibility
    of my ISP, which is fine - no problem. But, if this was the case, then my free domain (
    should be problematic as well. Lets see:

    250 sender OK

    No problems. There are also no problems using this address as the destination - messages sent to
    it are delivered immediately. In fact, the only trouble whatsoever is sending mail to AOL's servers,
    which is because my IP is dynamic.

    So with all this considered, what could be the reason I cannot send or receive mail to
    but I can do both flawlessly with

    The two domains obviously have different name servers. There must be something specific one has
    that the other doesn't. Something crucial! For starters, I noticed the name servers for
    do not respond authoritatively and allow recursive lookups; not to mention they received an F
    using the time lookup tool on The name servers for respond
    authoritatively, do not allow recursive lookups, and received in A+ on timing.

    If anyone understands this problem or can help me resolve it, please post! Or hell, you can even
    email me - but not to!

    Thank you


  2. #2
    AO French Antique News Whore
    Join Date
    Aug 2001
    DNS need 48 to 72 hours to be fully update around the world. That why is not update yet. Give it a few days and it'll be done. Your is allready update because is the DNS.
    -Simon \"SDK\"

  3. #3
    Junior Member
    Join Date
    Jun 2003
    Anything else? I don't think time is the problem. Its been well over a few days - almost a month really. I originally did not have an MX record for because the specification says by default if there is no MX then it will deliver mail directly. I just added an MX record (itself) and - nothing changed.


  4. #4
    Reverse dns should not have any affect on mail being delivered to your domain.
    It looks to me like the mx is correct, as long as the ip specified is the one for your mail server.

    I also sent a message to it froma a yahoo account, which hasnt bounced yet(like 5 minutes, only) it should be ok.

    Like SDK said, it takes a while for dns to propogate. A server which has never looked your domain up, and does so recursively should get the new information as soon as you change it(as long as it looks at the primary and not the secondary name server, and as long as the dns server is something that you controll, not a large isp's name server which only reloads zones a few times a day) but other servers which have looked up your site before, and have a cache, may take longer, it depends on the ttl and other settings on your primary dns server, as well as how the other dns servers are configured, how long they keep queries cached, etc.

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