For the Maine State Police Computer Crimes Unit, tracing the source of anonymous emails is a matter of connecting the dots. But it can take time to track electronic communications through a series of Internet service providers to find the unique address of a particular computer. A pair of analysts in the unit pushed to speed up that process this week when enlisted to help Windham police find out who sent two alarmingly threatening emails to school administrators in the Windham-Raymond district, which led to the closure of eight schools as a precaution to protect 3,300 students. “When it comes to this (Windham) call, everybody was concerned.