450 4.1.8 - Domain of recipient does not resolve

I’ve been having this every time I send a test email to myself.

What is the true cause of it and how can I fix it? I can’t find anything that explains it very well online.

DNS server handling your query: localhost
DNS server’s address:

** server can’t find www.ekmb.net: SERVFAIL

What do I need to change?

Please someone help. I have a really important email that isn’t working. I don’t want to lose jobs from clients and need to fix this over the weekend

It looks like you have some DNS problems of some sort… if you go to intodns.com for a report, you can get some info on the issue:


Based on that, it looks like the nameservers for ekmb.net aren’t responding… you’ll want to make sure BIND is up and running on your nameservers, and visible from the outside world.


Just a follow up - It ended up being my firewall that stopped my DNS server from resolving. Everything is working fine now.