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CName issue RRS feed

  • Question

  • Hello all,

    I have an exchange 2010, and we receive emails from most sellers without issue.

    Currently we are facing an issue with a customer who can not email us.

    When our customer sending an e-mail, he received the following report (CNAME lookup failed temporarily(#4.4.3).

    Please advise to avoid this problem.

     Thanks


    Thursday, February 22, 2018 10:24 PM

All replies

  • Hi,

    I notice that the issue only happens to one external user sending email to your Exchange 2010 environment. Please check if other senders who are in the same domain as this customer can send emails to you. Also try to send email from your Exchange 2010 to this customer and confirm if he can receive and reply it.

    Additionally, please check the DNS configuration in your Exchange side. For your reference:
    https://technet.microsoft.com/en-us/library/mt473798(v=exchg.150).aspx


    Best Regards,
    Winnie Liang


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    Friday, February 23, 2018 2:59 AM
    Moderator
  • Thank you Winnie for reply

    the customer received my email without any issue, but cannot receive his email

    also i asked his to send email from another user in the same domain but the problem the same 

    ?i need the evidence this issue not from my side what should i do

    regarding my DNS we are receiving emails from many customers

    thanks

    Friday, February 23, 2018 10:10 AM
  • I would suggest you first check there are no DNS issues, SPF issues, blacklist check for your domain/server

    I use mxtoolbox.com works great. if everything passes that is reasonable proof the problem is not on your side.

    Regards

    Friday, February 23, 2018 10:54 AM
  • Thanks for reply,

    yes i did test by"mxtoolbox.com" , it seem everything ok A record,DNS ,SPF,SMTP also my domain not listed in any blacklist , just there is issue in Cname and DMARC record because did not created .

    Do i need to create Cname record for my domain?



    Friday, February 23, 2018 1:29 PM
  • please check result of full test.

    Friday, February 23, 2018 1:38 PM
  • Are you violating  RFC1034 section 3.6.2 ?

    You cant have CNAME for root record

    try:

    host -t mx company.com

    should return MX records not CNAME


    • Edited by Bruce Tech Saturday, February 24, 2018 3:28 AM
    Saturday, February 24, 2018 3:12 AM
  • Hello Bure Tech,

    I did not understand , can you please explain more.

    host -t mx company.com

    Thanks

    Sunday, February 25, 2018 5:47 AM
  • Hi all,

    i need your help to overcome this issue.

    Thanks

    Monday, February 26, 2018 5:56 AM
  • Hello ,

    Also another customer complains, he can not send e-mail to us, but he receives from us

    any insight please?

    Thank you

    Thursday, March 1, 2018 11:25 AM
  • My apologies, that is Mac syntax, you can use nslookup;

    "NSLOOKUP <enter>".
    This will give you a ">" prompt.
    Type "set type=MX <enter>".
    Type "simpledns.com <enter>".
    You should now get the MX records for "simpledns.com"

    Here is some background info;

    https://serverfault.com/questions/91712/dns-using-cnames-breaks-mx-records

    Regards

    Monday, March 5, 2018 1:34 AM
  • Is second client getting same CNAME error in bounce?
    Monday, March 5, 2018 1:35 AM
  • Hi Bruce,

    I did Nslookup test 

    Non-authoritative answer:
    simpledns.com   MX preference = 0, mail exchanger = simpledns-com.mail.protectio
    n.outlook.com

    simpledns-com.mail.protection.outlook.com       internet address = 213.199.154.1
    06
    simpledns-com.mail.protection.outlook.com       internet address = 213.199.154.1
    38

    Is second client getting same CNAME error in bounce? yes

    Thanks

    Tuesday, March 6, 2018 6:28 AM