Southend ended a run of three successive draws with a 2-0 win against play-off chasing Rotherham at Roots Hall.
The Shrimpers, who had been beaten 5-0 by the Millers in August, went ahead after just seven minutes when Simon Cox played in Stephen McLaughlin to score with a neatly controlled left-footed shot.
Millers goalkeeper Lewis Price then stopped Marc-Antoine Fortune making it 2-0 when the striker was clean through on goal, before David Ball fired wide for the visitors on the stroke of half-time.
But the Shrimpers recovered strongly and doubled their lead in the 80th minute when Cox beat Semi Ajayi in the left-hand side of the penalty area before netting with a low shot for his first goal since Boxing Day.
The Millers still threatened, with Michael Smith having a header cleared off the line by McLaughlin before Towell hit the crossbar late on.