MX Record using DYNDNS sent emails to spam folders

Posted on 2009-02-17
Last Modified: 2012-05-06

I've installed Exchange 2007 SP1 on our server here, and published it via ISA 2006. I also have a domain However I could only get a dynamic IP from our ISP.

Thus I use Dyndns to keep track of my IP:, this is set in the modem router.

MX record (CNAME): (CNAME):

Everything looks fine except that emails it sent SOMETIMES went to spam folder and sometimes didn't. This has been happening intermittently and has caused frustration since I don't know if someone will receive an email I sent or not.
I read some articles about the destination mail server will receive my email as if it comes from host rather than .

Is there a way to address this problem ? Or anything else you can suggest apart from getting a fixed IP address.
Question by:Johnny_Nguyen
    LVL 24

    Expert Comment

    I would use a service like .. You can use a program like DirectUpdate to then publish the dynamic IP so that it would show as instead of the ..This is how we use to do it before we got a static IP.
    LVL 1

    Author Comment

    Thanks for the info. To be precise, when the emails I sent arrive in the inbox then they still show as (not dyndns), what I'm afraid is that in the process of sending, the destination host understand this as dyndns and categorise them as spams.
    Could your solution address this problem ?
    LVL 24

    Expert Comment

    Yes.. because it does see it different.. this should help with the problem.  Other thing I would do is use the ISP as a smarthost. If they can't do it then the dnsmadeasy has a option to buy for that too.. all pretty cheap.
    LVL 6

    Accepted Solution

    Another problem you might have with sending your own mail out is a lot of mail servers wont accept mail from Residential connections which I'm assuming you have since your on an dynamic address.  For example the pbl blacklist at is an list of residential IP that shouldn't be sending mail out.  Because of the increasing virus/spam being sent out from infected machines some email servers will simply drop the emails from residential or move them to an spam filter.  2 solutions to the problem either:

    1. Get an commercial internet connection with an static IP.

    2.  Have exchange smarthost all outbound emails to your ISP's mailservers

    The second option is the cheaper one and maybe the most problem free for you.
    LVL 65

    Expert Comment

    If you are on a dynamic address then you must send your email out through a smart host. That is the only way to get email delivered. The fact that you are using a dynamic DNS host for MX records has nothing to do with it. Receiving servers do not care. All they are looking at is the IP address of the server sending the email. If it is a dynamic IP address then it will either be blocked or flagged as spam.

    Set your Send Connector to use a smart host and enter your ISPs SMTP Server. If you don't know what it is, look on the ISPs web site for instructions for Outlook Express users and use the host they state for outbound email.


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