Washington (CNN)Employees at the company that maintained Hillary Clinton's private email server expressed concern among themselves about the way the former secretary of state's team directed them to manage data backups after the FBI started looking into the arrangements, according to emails obtained by a senator. In a letter obtained by CNN, Senate Homeland Security and Governmental Affairs Committee Chairman Ron Johnson, R-Wisconsin, asks Datto, Inc, the makers of Clinton's server back-up system, for information on how her emails were preserved and protected. The FBI has also sought information from the company, according to sources. Johnson indicates that a "Clinton...