MacDonald was dismissed in the first half of the Millers’ damaging 3-0 defeat to Shrewsbury last week, with referee Antony Backhouse ruling that the centre-half had used an elbow in an aerial challenge.
After seeking counsel the club chose to appeal the decision, but it was upheld by an FA disciplinary panel.
MacDonald will miss three League One games but will be available for the Papa John’s Trophy final at Wembley next Sunday.
“I watched the incident back, took some advice off people and decided to appeal,” said manager Paul Warne.
“Angus hasn’t moved his elbow to cause damage. He’s legitimately gone up to win the ball. He’s got his arm in front of him. You see worse than that with throw-ins down the line.”
“We didn’t make a frivolous appeal. We wouldn’t do that because we know the risk of it.”
Warne is happier about a switch in schedule over the Easter weekend.
The Millers were due to host Ipswich on Good Friday and then visit Burton on Easter Monday, but their home game with the Tractors Boys has now been moved to the Saturday for TV coverage.
The Burton game has been pushed back 24 hours and Warne is pleased as they travel to Portsmouth in the midweek before the game against Ipswich.
“I’m very happy with that,” said Warne. “Playing at Portsmouth on a Tuesday night, getting back at God knows what time and then facing Ipswich on the Friday wouldn’t have been easy.
“In elite sport especially, there is no better recovery than sleep. The more periods of sleep you can get in between games, the better.”