554 5.4.4 Could not resolve remote host


  • We are using Exchange 2013, external user receives following error when sending email to our user:

    This is the IdeaMailServer program at host

    A message that you sent could not be delivered to one or more of its<o:p></o:p>
    recipients. This is a permanent error. The following address(es) failed:<o:p></o:p>

    <>: 554 5.4.4 Could not resolve remote host - RR Set that should exist does not

    Any ideas what could be wrong?

    Friday, June 23, 2017 10:59 AM

All replies

  • Hi,

    Does this issue only affect this specific domain?

    If so, it's recommended to check if you have blocked this domain/IP addresses in your block list.

    Please check if there are the same errors when that domain send messages to another domains.

    Hope it helps and thanks for your effort.


    Jason Chao

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    Monday, June 26, 2017 9:44 AM