Network Host unreachable

Might be a problem with the network card and kernel, add this to grub.conf

acpi=off noapic


to the end of the KERNEL line.

DNS errors when sending mail thru PHP

Login to server via SSH and delete the file /etc/eximmailtrap if it exists. Secondly, edit the file /var/cpanel/cpanel.config and change eximmailtrap=1 to eximmailtrap=0.

Restart the mailserver and there you go