You may have some defenses, an email of the alleged claim is not usually proper notice under most leases. If the landlord claims you breached the lease by moving out then the landlord has a duty to re-rent to mitigate the damages.
Sometimes landlords will wait until the expiration of the old lease to total a bill. You should gather all of your evidence and get ready in case the landlord sends the account to collection. Or tries to sue you directly. If the landlord takes real action then you will need your evidence to defend yourself. Do not engage the landlord in a discussion if necessary have a lawyer write a letter or answer the lawsuit.
Please be sure to indicate the best answer. If this answer was helpful, please mark as helpful below. Only. If and until you and I sign an Agreement for Legal Services, I am not your attorney. These answers are provided for informational and/or novelty purposes