I'd say a non-tech user has no idea what a server or cache is. I'd go with the word "backup" instead. Something like telling them that email is not backed up (o

I'd say a non-tech user has no idea what a server or cache is. I'd go with the word "backup" instead. Something like telling them that email is not backed up (online? where?) and if they delete it from their computer it won't be able to be recovered.