Exeter suffered a blow to their League Two promotion hopes as Scott Doe sealed victory for Dagenham & Redbridge.
Defender Doe nipped in at the near post to emphatically head home a corner with the game still in its infancy.
Exeter struggled throughout although Jordan Seabright had to be at his best to save Craig Woodman's free-kick.
The win puts Dagenham five points clear of the drop zone but seventh-placed Exeter's third loss in a row left them within range of their play-off rivals.
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Exeter manager Paul Tisdale told BBC Radio Devon:
"The players put a huge amount of effort in, but it was very disjointed. The decision-making was impaired by anxiety and frustration and a bit of panic.
"I'm quite philosophical about the whole thing. I'm desperate to get in the play-offs but we're finding it very hard at the moment.
"I'm sure people are going away thinking 'that's it' and that it's all over but it's not.
"It will go to the last game, I'm sure, and we have to attack Tuesday's game the best way we can."