Forum Discussion

djplagzilla's avatar
New Contributor II
3 years ago

Cxdns error when sending mail from my Outlook 365 account.

Cxdns error when sending mail from my Outlook 365 account. Is Cox blocking use of Outlook? Appears that Cox use of Cloudmark is filtering/blocking my outbound messages. I’m not sending bulk emails! Only sending a few a day! I talked to Cox and they said couldn’t help unless I signed up for their $10/month service option???! 

10 Replies

  • DavidA2's avatar
    Former Moderator
    Hi Djplagzilla,

    I am sorry to hear that you are having trouble sending emails. I am not aware of any known issues with email right now. Are you able to provide the exact error that you are seeing?

    Cox Social Media Specialist
    • djplagzilla's avatar
      New Contributor II

      The error is

      Task ' - Sending' reported error (0x800CCC6F) : 'Your outgoing (SMTP)email server has reported an internal error. If you continue to receive this message, contact your server administrator on Internet service provider (ISP). The server responded: 554 cmsmtp blocked. Refer to Error Codes section at https:/ for more information. AUP#CXDNS'

      • JonathanJ's avatar
        Former Moderator

        Are you having any issues sending from cox webmail? This link will also provide the outgoing setting for outlook 365

        Jonathan J
        Cox Moderator
    • djplagzilla's avatar
      New Contributor II

      And I just got off a support chat with Microsoft for approx 1 hour and they tried everything. They suggested I get back with Cox. 

      • CrystalS's avatar
        Former Moderator
        Hi @Djplagzilla,

        I am so very sorry to learn of your email troubles and I'd like to help.
        This appears as if you may need someone to look into your account. We would definitely be able to assist you with this. Please reach us on Twitter at @CoxHelp, visit us on Facebook, or email us at Provide us the name on the account with the complete service address with a link to this thread so we can get started.

        Crystal S.
        Cox Support Forum Moderator
    • MichaelJ's avatar
      Hi Dmoranok,

      Are you able to send/receive emails using Cox Web Mail after you are logged on to the Cox website:
      This link may prove helpful as it lists the error codes and suggests steps to take:

      If you were unable to resolve your problem using the steps in the Error Codes section, send us an email at for assistance. Please scroll doen to the bottom of the article for the requisite information needed in your email.

      Thank you,

      Mike J.
      Cox Support Forums Moderator
      • djplagzilla's avatar
        New Contributor II

        I finally figured this out. I disabled/turned OFF the McAfee VPN option and now I am able to send emails!

        Just guessing here but the VPN option must have been changing my IP address and Cox was thinking this was a blacklisted IP???

        Not sure of the technical details but everything is working again!