Orient cruised into the second round with a powerful display to sink brave Dagenham & Redbridge in this derby cup duel.
First-half goals from Matthew Lockwood and David Hunt plus a third just before the hour from Wayne Carlisle put Orient firmly in the driving seat.
But the brave non-league visitors refused to throw in the towel and substitute Chris Moore netted a consolation with a twice taken penalty seven minutes from time.
Any hopes of a FA Cup giant killing quickly disappeared as Orient took the lead in the 11th minute.
Defender Lockwood, who passed a fitness test before kick off, fired home from 25 yards after the Daggers failed to clear Hunt's long throw.
Orient continued to press and Michael Simpson had an effort well saved by Tony Roberts and the ever dangerous Jabo Ibehre saw the follow up blocked.
But Daggers weathered the storm and almost levelled as first Stuart Douglas saw his effort blocked by home goalkeeper Lee Harrison and minutes later Harrison saved splendidly from Mark Janney following his excellent solo run.
Orient regained their composure and Carlisle shot just wide before the home side added a second on 37 minutes when Lee Steele's cross was headed home via a post by Hunt.
After the break Janney should have cut the deficit as the Orient defence waited for an offside flag that never came while Douglas also had a shot blocked.
But Orient wrapped things up when Ibehre and Hunt combined for Carlisle to net a third from close range.
John Still's side showed great resilience as they tried to claw their way back into the match and their efforts were rewarded in the closing minutes when Orient defender Gaby Zakauni fouled Craig Mackail-Smith in the area.
Daggers' substitute Moore kept his nerve and netted with a fierce shot past Harrison's right hand after referee Mike Thorpe ordered the first kick to be retaken following encroachment by the visiting players.