I don't think that one email will qualify for harassment. However, you can certainly report the email to the local authorities and then keep all communication from him. If it continues, have him arrested and obtain a new OP. She should not respond to communicate with him at all.
She can file a police report and can also re-file for an order of protection. If he contests the order of protection, however, the problem she may face is lack of proof. She can always contact her e-mail service provider & see if it was saved on their system. In any event, I encourage her to schedule a consultation with an Orange/Westchester Co. Domestic Violence attorney.
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Two options gather more information and file for an order of protection later when you have enough evidence or file now and see if he will consent to an order of protection when the case goes to court.
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