If the DNS for your hostname is not set up correctly, you may receive an email saying something similar to this:
Your hostname (srv.yourdomain.com) could not be resolved to an IP address. This means that /etc/hosts is not set up correctly, and/or there is no dns entry for srv.yourdomain.com. Please be sure that the contents of /etc/hosts are configured correctly, and also that there is a correct 'A' entry for the domain in the zone file. Some or all of these problems can be caused by /etc/resolv.conf being setup incorrectly. Please check that file if you believe everything else is correct. You may be able to automatically correct this problem by using the 'Add an A entry for your hostname' option under 'DNS Functions' in your Web Host Manager.
Most of the time, this error email is triggered by private name servers not being set up correctly, or that no DNS record can be pulled for the hostname 'server.yourdomain.com'. It could also mean there are missing, corrupted or improperly formatted DNS records.
Private Name Servers
If you are using private name servers then please check the following items to ensure accuracy:
Generic Name Servers and A records
If you are not using private nameservers, or your private nameservers are set up correctly, then you may be missing the A record for your hostname. To check:
Log into WHM
Click DNS Functions
Click the Add an A Entry for your Hostname option
If an A record exists, it will be shown there; make sure it shows the correct IP address (contact Support if you are not sure)
If no A record exists click the Add Entry button to add the IP, making sure the correct IP is listed there before continuing to add the missing A record
Note: on a Dedicated Server or VPS, you would also want to make sure the hostname exists in/etc/hosts as well.
See also Log Into WHM, Set Up Custom Nameservers