Hi,
To narrow down the issue, please try the following changes in Exchange:
1. Restart the Microsoft Exchange Transport service.
2. Please run the following netsh winhttp command from a command prompt to verify proxy settings existed:
netsh winhttp show proxy
If the proxy is not existing, run a Netsh command similar to the following to specify the proxy server:
Netsh winhttp set proxy proxy-server="http=%ProxyServer%;https=sproxy:88" bypass-list="*.domain.com"
After doing so, try running this command to kick off an update:
Update-MalwareFilteringServer.ps1 Identity %ServerName%
3. Verify the NT AUTHORITY\Network Service account has Full Control permissions on the <drive>:\Program Files\Microsoft\Exchange\V15\FIP-FS\Data\Engines\amd64\Microsoft\bin directory.
4. try to manually download engine and definition updates:
http://technet.microsoft.com/en-us/library/jj657471.aspx
If possible, please provide the exact text shown in the General tab of Event 6027 for further analysis.
Regards,