I've finally decided to start the M.A. Math program at my university. It's designed for those who want to teach math at a junior college, but I have no plans to do except maybe for "retirement" later in life. It's not a science/research degree, but I want to learn more mathematics, primarily the classes I didn't take in undergrad (complex analysis, differential geometry, etc.) For the application, I'm supposed to provide three references including at least one from a professional mathematician. I never developed a familiar relationship with one of my professors to warrant a recommendation. However, I have emailed two professors with no response. The second I might just have to stop by his office if I ever get a chance - I work full-time and it's not really practical. When I took two of his classes, he made it clear that he doesn't check email, but I figured that he would have to for inter-and intra-departmental correspondence. How exactly should I proceed in procuring a professional mathematician's recommendation?