I have used faxed proxies in the past without a problem.
Our lawyers from Guzman never had a problem with that.
Why would the "administration" try to prevent you from carrying a proxy?
It is not for your administrator, who is supposed to working on your behalf, to decide that you can not use a proxy.
It is for your lawyer to decide.
Ask a lawyer or look in the Dominican Condo Laws.
Then show your admin your results and tell them where they can put the proxy !
In fact I even used an email with no signature since an owner abroad did not have a scanner. They simply wrote that I could vote on their behalf and that was acceptable.
