The Pirates have won twice in 13 games since Penney replaced Paul Trollope and this was seen as a must-win game, but a stunning free-kick from Danny Green after Jerel Ifil had been sent off for a 44th-minute foul and an unmarked header from Romain Vincelot gave the Daggers' survival hopes a huge boost.
Penney said: "Everything seems to be going against us at the moment. I haven't seen the other results, but as things stand the odds are against us staying up.
"We can't afford to give up and we won't do so. The players are very down in the dressing room, but we will pick them up and go again at Tranmere on Tuesday night.
"I have no complaints about the sending off. I have seen the tackle again and Jerel didn't get anything on the ball.
"We started the game brightly, but going down to 10 men hurt us and the second goal was outrageous. Allowing a player to head in unmarked at a corner just isn't acceptable."
Source: PA
Source: PA