Symptoms
- 
Domain hosted on the server fails to be resolved over DNS: # host example.com 
 Host example.com not found: 2(SERVFAIL)
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The following error can be found in the /var/log/messages(or/var/log/syslogon Debian/Ubuntu) file:named[14109]: zone example.com/IN (signed): journal rollforward failed: journal out of sync with zone 
 named[14109]: zone example.com/IN (signed): not loaded due to errors.
 named[14109]: zone example.com/IN (signed): receive_secure_db: out of range
Cause
The issue is related to the inconsistency of the BIND cache.
 Possibly it is caused by the BIND bug.
Resolution
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Go to Domains > example.com > DNS Settings 
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Click Disable and then Enable