Is it unprofessional to communicate to a board member about a comment in an email about a work situation?

I work in a small organization with 7 employees and about as many board members. There has been an ongoing "saga" regarding a vendor who hasn't been honoring a service agreement which has all been communicated via email. One of the board members, the Exe. Dir. and 4 or 5 people are all on the emails that have been flying back and forth for several months about this issue. I was instructed to read all the emails and get involved to get this vendor to honor the service agreement. This week, after two emails from me (to ALL on the email list), I wrote to the president and the only other person I've ever actually spoken to from the vendors side, with a cc to the exe. dir. and the board member saying that I feel that contacting the better business bureau may be our only option, since the numerous emails have been ineffective. The board member responded to me directly within only a few minutes saying that he was on the lookout for a new vendor and to keep pushing. The next day the board member sent another message saying that future communication to vendor should not be as "aggressive". I responded directly to board member saying that I was surprised by the second email and then said that perhaps I was mislead from my side (meaning the exe. dir.), that perhaps I didn't have all the information, since I did not have a copy of the contract and that I felt the involving me was counterproductive since I don't have this information. Board member responded to me saying that he TOTALLY understood my frustration, along with another sentence I can't remember at this moment. He signed it with, "No worries". Now, my boss (exe. dir.) is furious at me for being "unprofessional" about both emails and for "going off on a board member"
in regards to the emails directly to the board member. What do you think?