Warning: Unable to resolve hosts on the Internet. Unable to resolve hosts on the Internet for at least one DNS server! This may result in e-mail loss. Please review network settings and correct them.

This message says you are having problems with at least one of your DNS servers. DNS resolution is required for e-mail analysis and delivery, so there may be a problem affecting your e-mail flow. To see the validation error report go to the "Reports > Server Status" page and look at all of the validation results. There will be lines for each DNS server saying "Querying DNS server" with the results.

Try the following:
1) Reboot your local DNS Server
2) Restart your MTA using the PerfectMail Dashboard

After restarting these services go to the web administrator interface "Tools > DNS Lookup" page. Enter the IP address of the questionable DNS server and lookup names for domains that you would not normally see. The idea is to try and find domain names that would nor normally be cached on your DNS server.

Sometimes we see DNS servers misbehave when performing new lookups. When this happens  DNS lookups for cached entries appear to work fine, but new lookups appear to fail. Restarting DNS services appears to fix this problem in the short term.