It is also worth reminding the sender of the threatening emails that by sending them to the Secretary that they will form a permanent part of the OC records.
And that any other owner is entitled to see them, as is any other person entitled to access the OC records. This includes potential purchasers of units. Maybe even mention that the emails could inhibit the price paid for units being offered for sale.
And, especially important, the dispute goes to an external organisation, including NCAT then those emails will form part of the record of matters being disputed.
Therefore it behoves the sender to remain civil, factual and to seek to resolve their dispute timeously.