Reminds me of the Petraeus scandal where they communicated via unsent Gmail drafts in a shared account.

EDIT:

From https://en.wikipedia.org/wiki/Petraeus_scandal

    Petraeus and Broadwell used fake names to create free webmail accounts
    exchanging messages without encryption tools.
    They would share an email account, with one saving a message in the
    drafts folder and the other deleting it after reading it.