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In this case he does not have authority to suspend you. You Are equal partners here.
If there is any sort of operating agreement or company bylaws that is the first place to see who has what authority. The use of the company email does gove rise to some concerns and might be enough to suspend him from any role he has but he would retain his ownership interest. The Board could collectively vote and address the situation. However without knowing all the details of the situation they should act when the picture is clearer.