While downloading rapid release definitions with Symantec Messaging Gateway (SMG), the following error appears in the log:
"Download failed with error 28. URL: http://definitions.symantec.com/defs/rapidrelease/ennlu.lin"
Error: "Download failed with error 28. URL: http://definitions.symantec.com/defs/rapidrelease/ennlu.lin." in JLU-Controller log.
The error code 28 in the JLU Controller logs indicate a network timeout.
SMG is unable to download the complete antivirus definition package before exceeding the download timeout. The network connection may be too slow or too congested to fully download the anti-virus definitions.
If you are configured for Rapid Response Updates, change the LiveUpdate configuration to Automatic updates on the following schedule and increase the timeout value.
If this is a recurring issue, the only remaining solution would be to position a LiveUpdate Administrator (LUA) server on a location in the company network that has fast access to the Internet. This LUA server can download the definitions that SMG needs and distribute them to an internal location that the SMG can access quickly. The SMG can then be configured to retrieve content from this internal Distribution Center (DC), rather than from the Internet LiveUpdate source servers via (Malware > Liveupdate > Download virus definitions from a LAN host).
Please see Install and configure LiveUpdate Administrator for details on setting up an internal LUA server.
And How to configure Messaging Gateway to download virus definitions from a LAN host on how to configure SMG to download definitions from LUA.
You can download the latest version of LUA in the article Download LiveUpdate Administrator.