The old costly habits reared their ugly head again as the Daggers slumped to a disappointing defeat.
Hopes were high after the good run Wayne Burnett's men had been on and the Daggers were looking to win three games on the trot for the first time in six years.
But those hopes were dashed by the sort of poor defending that had made life so difficult for the team earlier in the season.
Southend's first two goals should certainly have been prevented and once they went in the Daggers were up against it.
The opener came from the lively Joe Pigott in the 16th minute. He was allowed to collect a pass and wriggle through two attempted tackles before driving the ball home.
The Daggers were level within six minutes and the in-form Billy Bingham
played a big part in the equaliser.
He whipped in a great free kick with his left foot and Ayo Obileye
met it on the far post with a header that gave keeper Daniel Bentley no chance.
It was an even contest at that stage. But more poor defending allowed Southend to regain the lead with virtually the last kick of the first half.
As the ball was played into the Daggers box a weak header sent it straight to Ryan Leonard, lurking 20-yards out. He took full advantage of the gift by lifting the ball over keeper Liam O'Brien
and into the net.
It was game over when Southend got their third from the penalty spot in the 51st minute. Luke Prosser met a deep cross from the right with a header that struck Damian Batt
's upraised hands and Barry Corr fired in the resultant spot kick.
Southend took total control after that and always threatened to add to their tally.
The only time they bothered Shrimpers keeper Bentley came two minutes from time when teenage substitute, Jodi Jones brought a superb one handed save from him with a well struck effort that was heading for the top corner
Dagenham & Redbridge: O’Brien, Batt, Doe, Obileye, Widdowson, Howell (Jones 86), Bingham, Boucaud, Hemmings, Fenelon (Jakubiak 56), Cureton.
Unused substitutes: Moore, Ogogo, Labadie, Gayle, Yusuff.
Southend United: Bentley, White, Coker, Thompson, Prosser, Worrall, Timlin (Deegan 83), Corr, Hurst (Weston 81), Leonard, Pigott, (Cassidy 89).
Unused substitutes: Smith, Atkinson, Payne, Binnom-Williams.
Attendance: 3,393 (1,455 Southend United supporters)