The email was worded in a way that would allow HBO to stall for time while it assessed the situation, Variety reported, citing a source close to HBO's investigation.
HBO also requested the hackers to extend a ransom payment deadline by one week, Variety said.
The Guardian and other publications reported earlier this week that hackers had posted some stolen HBO files online, demanding a bitcoin ransom to prevent additional releases.
HBO did not immediately respond to a Reuters request for comment.
The hack has come at a sensitive time for HBO, whose parent Time Warner is awaiting regulatory approval to sell itself to AT&T Inc (T.N) in an $85.4 billion deal announced in October.
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