Thanks for all the info. The issue appears to be to do with Exchange Transport Agent priority. As we are moving away from AVG and more into the Exchange side of things, these steps should resolve the issue but we won't support any issues that may arise from the outcome of these steps, unless AVG related of course. The below steps were performed in test environment running Hub Server only.
If you go into the Exchange Management Shell and run the 'get-transportagent' command, all installed Transport Agents will be displayed along with their priority. If the 'Content Filter Agent' has a higher priority than the AVG agents, then the messages may be processed by content filtering before AVG has inserted the [SPAM] tag into the email subject.
Unless you are using the other aspects of the Exchange Antispam, the other Antispam agents installed when the 'install-AntispamAgents.ps1' script was ran can be removed (Connection Filtering Agent, Sender Id Agent, Sender Filter Agent, Recipient Filter Agent, Protocol Analysis Agent). If they aren't being used run - uninstall-transportagent "Name of agent" to remove the unused agents.
To change the agent priorities, run this command to assign the priorities so the 'Content Filter Agent' has a lower priority than the AVG agents - Set-TransportAgent -Identity "Name of Agent" -Priority 12
Once done, the agent priorites should look something like the screenshot in the post depending on what other agents are running on the Server. Restart the Transport service - restart-service msexchangetransport.
All being well, all messages marked as [SPAM] should now be redirected to the quarantine folder.
Some of genuine incoming emails to our server are being tagged as spam emails even I have whitelisted sender's email address domain (@anz.com) in AVG Server components settings. I have attached our transport agent priorities. Please advice what I should do to solve this problem?
Unfortunately it is not possible to do anything with the spam emails from within AVG. They are forwarded on to the clients by design. The Content Filtering part of Exchange can be used to filter any messages with [SPAM] in the subject. Please visit this link for details - http://technet.microsoft.com/en-us/library/bb124490.aspx
Hi, I would like details of content filter config to quarantine emails tagged with [SPAM] by AVG?
The below blocks the emails altogether.
Add-ContentFilterPhrase -Phrase "[SPAM]" -Influence BadWord