Documentation exists that former Secretary of State Colin Powell and Hillary Clinton communicated around the time Clinton began her term as Secretary of State. He gave her advice from his experiences on using a private email server rather than a more secure email server. He did nothing to abet Secretary Clinton in wrongdoing, if there was any; however his perspectives may have influenced her behavior which has been deemed "careless".
Clinton was really the only person involved in the Clinton email scandel except for a few DNC members and interns who tried to cover up the whole thing before it got out of hand and cost Clinton the possibility of winning the race and earning the nomination, so there was not really a scandal.
From what I know, Colin Powell only insulted and said bad things about Hillary Clinton in his own private emails. Though he is also a former Secretary of State, I do not believe he was involved in the Clinton email scandal, unless there is shown to be evidence that he was.
Colin Powell admitted that he advised Hilary Clinton to use a personal email address for personal emails, but he told her to use a government server for classified messages. He repeatedly told her and her aides not to try to implicate him in her scandal because he never set up a private server and he never suggested that it would be acceptable for Clinton to do so.