We help IT Professionals succeed at work.
Get Started

DNS Query Failed on single record

Last Modified: 2012-05-12
We are running Windows 2008 SBS Standard, which has been up for about 3 years. Email is flowing with the occasional hicup. On Monday a customer upgraded to Microsoft Office 365 and now hosts there email at Microsoft. Emails to that address are getting a delayed delivery message back to the user with the Last Error of:

451 4.4.0 DNS query failed.

I have tried:
    - Testing the nslookup and it is returnning the A record fine.
    - Have Flushed the DNS    ipconfig /flushdns
    - Cleared the DNS cache
    - Tested the SMTP server from MXtoolbox and it is working although giving the warning:
         Warning - Reverse DNS does not match SMTP Banner
    - Even added a mx record to my local DNS zone for the domain.

Any thing else to try?

Watch Question
Top Expert 2011
This problem has been solved!
Unlock 1 Answer and 7 Comments.
See Answer
Why Experts Exchange?

Experts Exchange always has the answer, or at the least points me in the correct direction! It is like having another employee that is extremely experienced.

Jim Murphy
Programmer at Smart IT Solutions

When asked, what has been your best career decision?

Deciding to stick with EE.

Mohamed Asif
Technical Department Head

Being involved with EE helped me to grow personally and professionally.

Carl Webster
CTP, Sr Infrastructure Consultant
Ask ANY Question

Connect with Certified Experts to gain insight and support on specific technology challenges including:

  • Troubleshooting
  • Research
  • Professional Opinions
Did You Know?

We've partnered with two important charities to provide clean water and computer science education to those who need it most. READ MORE