Corrected entry: A message encrypted with Mercury is shown in the email to the Einstein account. The message does not look like it has been produced with a proper encryption algorithm since there are long sequences of letters that are repeated (e.g. GSDX2BYAC52...). A property of all encryption, regardless of algorithm, is by definition that the output be random.
Corrected entry: When trying to get into the Einstein email account, Jeffries suggests using the password "E equals MC squared, all caps". If the FBI only accepts uppercase characters then he doesn't need to qualify his suggestion. If the FBI is sensible and allows lowercase letters then Jeffries suggestion is incorrect; the 'm' and the 'c' in the equation stand for mass and the speed of light respectively and these conventionally are represented by lower case letters.