Upvote:1
Searching the flight number on Google will typically indicate the departure terminal, e.g. for Qatar Airways QR 738, which departs from SFO airport:
Otherwise the departure airport will very likely have the information as well. https://flightaware.com/live/flight/QTR738 is another source.
Upvote:2
Terminal A
Delta uses exclusively Terminal A in Boston (unless it's an international arrival which go through immigration and customs at Terminal E)