Actually, once everybody calms down (and grows up a bit) exactly what is threatening about this alleged email? You signed a contract and in that contract it would have spelled out details of any bond involved and notice period required. You give the notice period required and if you owe bond money then you come to an arrangement to pay it back.
Some years previously I left an airline owing bond money. I was moving 'onwards and upwards' and the company I was going to would probably not have taken me if I offered to 'jump ship' I gave the 3 months notice, informed them that I would pay the bond and we agreed when/how it was to be paid. I continued to do my best for them up until my last flight and was rewarded with a glowing reference.
If you're either not planning on leaving or are leaving but plan on fulfilling your contractual obligations, what's the problem? Like another poster, I have been in aviation for nearly 40 years. Seen it all, done most of it and nothing much has changed.
One final thought. Not too sure about posting what is surely a confidential email on a public forum.