I am a UK based contractor that has a contract with a NJ based company to provide my services.

First, I will assume that the contract is governed by NJ law.  I know nothing about UK law, and it may be very different. The fact that the contract could be terminated for any reason upon 30 days written notice does not mean that it could not be terminated for other reasons which do not require 30 days written notice.   For example, if you had materially breached the agreement in some respect, there is nothing in this clause which would require the other side to give you 30 days written notice in order to terminate.  That being said, if a judge or jury holds that there was no other ground for termination, you should be entitled to 30 days notice, and to recover any damages you suffered due to the failure to give you such notice.  I view the email versus snail mail to be immaterial (particularly if you customarily dealt in emails), but some Court might view it differently and give you a few more days damages due to the failure to follow the procedure set forth in the contract.