The Boston office of the Securities and Exchange Commission has been asking mutual fund firms and their advisers how they vote proxies. In a letter sent in November with a Jan. 6 response deadline, the SEC sought copies of proxy statements and of securities lending and borrowing agreements, as well as proxy-related e-mails to help determine whether there were any conflicts of interest when it came to voting at companies in their portfolios. Observers say the data requested is just to see how well funds are complying with SEC rules.