As email has become a primary form of communication, more and more nonprofit boards are taking action by email vote. I personally believe email voting is an efficient method of board approval for very specific questions where little or no discussion is necessary. Unfortunately, most states have declined to adopt specific legislation regarding email voting.
Without a special rule, email voting likely constitutes voting by written consent. Unlike in-person or telephonic meetings that only require a majority vote to approve a resolution, most states require a unanimous vote of all the directors in order for a written consent to be effective.