WRITE (uses quota): start tracking up to 10 tracking numbers per call. Each ACCEPTED number costs 1 quota from this account (see track17_get_quota); rejected numbers cost nothing. Deleting and re-registering a number costs again. 17TRACK then updates the status itself every 6-12 hours; read it with track17_get_tracking. The carrier is detected automatically unless a carrier code is given. No e-mail notifications are enabled. POST /register.