I've made it personal policy to not return unexpected emails immediately. I might read the email, but I won't immediately respond to it or address it if it is not a priority by my reckoning.
I don't even decline last-minute unsolicited meeting requests until the next working day. As a salaried professional in upper management, I believe that I've earned the right to manage my time and resources as I see fit. Fortunately, I work for an executive staff who agree with me, so the others who disagree with MY standards for time management are, invariably, told to pound salt.
I also hate phone conversations that will set some sort of precedent. I'm perfectly content to collect data to make a decision via phone conversation (I will often also rehash the conversation via email to give the other party an opportunity to clarify or readdress my perspective), but I do not like to debate a position in a voice conversation unless I'm very well prepared. It's probably just my communication style, but I'm aware of my fallacies and try to adjust my processes to minimize their impact.
Of course, having said all that, true emergencies exercise all potential exceptions. Again, I've earned the authority to determine what constitutes an emergency. My CEO might complain about the order in which I address his concerns, but he grants me the discretion to do so. (Yes, I know I'm very fortunate in that regard.)