Exeter managing director Ian Huxham said the club has not yet begun to calculate the financial worth of drawing United he is still in a state of shock:
Huxham said: "It is not really possible to put into words what this means, but if any football club deserves it, it is Exeter City for the hard work thousands of fans have done over the last 18 months. This one's for them, they have kept the club going."
"I haven't been able to get a handle on the financial implications of the game, but I have heard a lot of estimates from people within the game. It will go a long way towards paying off the debt, but that's not job done. It will not guarantee the safety of the club in the long-term but it is a huge help. The future of the club is still in the hands of the fans."
United have only played Exeter once before and that was also in the third round in 1969, when goals from John Fitzpatrick and Brian Kidd, plus an own goal secured a 3-1 victory.
Exeter were in the League then and the last time United played a non-league side was in 1953, when Walthamstow Avenue visited Old Trafford drawing 1-1 United won the replay, at Highbury, 5-2.