I am now applying for postdoc (mathematics) and starting to search for jobs in mathjobs. In quite a lot of situation, the job description ask for three letter of recommendation. My question are:
When they ask for three letter, for example here, can I have 4 or 5 letters sent to that university? (I planned to have 3-4 letter for research and 1 for teaching).
If I can only send three letter, is it preferable to have 3 letters all focusing on research aspects, or 2 on research and 1 on teaching (assuming that that postdoc job requires one to teach)?