Ok its not a content filtering issue, looking into it a bit more some devices are reporting in fine and others are not. I cannot find a pattern as the OS is the same for most devices and they way they are all connected to the network is a the same i.e. wired with same IP range.
I have allowed all of the ports as mentioned in the Kbase. One thing that is odd is that it needs from 993 which is normally used for IMAP.
I have uninstalled agent and reinstalled it to no avail.
I have opened a ticket but support have just replied asking me to call them which isn't helpful.