3 Replies Latest reply on Oct 20, 2014 10:19 PM by dingleaaron

    451 Error: All MX servers unavailable for domain


      Hello everybody,


      Begin from last Monday, our SaaS met below Error information (both scbmc.com and cn.cbpg.com), Many Emails met deadly delay delivery, especial on busy-hour。



      Recipient Disposition: [250 Deferred; Mode: normal; Queued: no; Frontend TLS: yes; SPF: n/a]
      Message Disposition: [451 Could not verify recipients (41d97725.0.2281467.00-2369.3360274.s14p02m001.mxlogic.net): All MX servers unavailable for domain scbmc.com (Mode: normal); Backend TLS: n/a; Backend IP: n/a; Policy Set: Default Inbound]



      The MX recorder is normal :








      Not all emails met this error, sometimes it happened and email would be delay deliveried (delivery fail & report error message many times).  I don't know what cause these.


      Our trail license was expired on Oct 15, and Oct 28 these errors begin happened. today we finish the purchase process and get the license, but there errors still exist.


      So pls help me to analyze the reason and solve these.

        • 1. Re: 451 Error: All MX servers unavailable for domain

          Hi there,


          Same problem https://community.mcafee.com/thread/62120


          looks like for some reason SAAS cant find a valid Backend IP....


          Keep you posted though opening a case might be good idea.



          • 2. Re: 451 Error: All MX servers unavailable for domain
            Brad McGarr

            Hi Sergio,


            In general the error indicates the recipient server we are attempting to connect to is refusing the connection for some reason, whether because the server is down or it is greylisting the IP. We would need to know more specifics though to determine exactly what is going on. A situation like this, I highly recommend contacting the Support Team that works with your account for additional troubleshooting.

            • 3. Re: 451 Error: All MX servers unavailable for domain

              Just wanted to let you all know that I had the same problem with a local 2010 Exchange Server and McAfee.  I got it all to work today as I created a different type of receive connector in Exchange.  McAfee gives you a list of the CIDR's to add as IP/21 or IP/24, but  when I put these on the server's receive connector I could not get it to work and I got the error above."Message Disposition: [451 Could not verify recipients"  Instead of entering these in the receive connector I choose the option to add IP and SubMask on the Exchange server for the receive connector.  Enter the IP and then the Subnet Mask EX: and SubMask:  I also created a new Receive connector on the Exchange server and added only these IP's on Port 25.  I then move MX records and email is now flowing. 


              Again all I did was create a different type of connector with IP and Mask and then created new Receive connector.  All is working for me now!