The long answer is that there is no "server"—there are many different servers and pieces of internet infrastructure in question, and the United States intelligence community and independent security researchers have examined much of it and have all reached the same conclusion: Russia hacked the DNC.
It is widely believed that CrowdStrike, a cybersecurity firm hired by the DNC to respond to the hack, gave an identical image of some of the servers to the FBI, which experts I’ve spoken to say would be more useful than giving the FBI a physical server itself. I say “widely believed,” because we don’t know exactly what CrowdStrike gave to the FBI. However, in March 2017, former FBI Director James Comey told Congress that the
FBI got an “appropriate substitute” from CrowdStrike, and Mueller’s indictment makes clear that the FBI has lots of information about the hack from both within the DNC and from other sources.
GFY - PLEASE.