I've been on an obscure media hunt for the longest, and there is probably a good reason I haven't found it.
Many years back, it would have had to been before her first run, there was a clip of HRC sitting in the back of a limo commenting on someone getting busted over an email server.
Nothing groundbreaking and IANAL, but it would put her on record of being knowledgeable of email servers before she claimed to be.