1. A non-transitory computer readable medium comprising program code executable by a processor for causing the processor to: receive an electronic communication usable for training a neural network and comprising a plurality of characters; receive a sentiment dictionary comprising a plurality of expressions mapped to a plurality of sentiment values representing different sentiments, each expression of the plurality of expressions mapped to a corresponding sentiment value of the plurality of sentiment values; determine an overall sentiment for the electronic communication using the sentiment dictionary; automatically construct training data usable for training the neural network based at least in part on the overall sentiment of the electronic communication, wherein the training data comprises a plurality of overall sentiments associated with a plurality of electronic communications usable for training the neural network; train the neural network using the training data; receive a second electronic communication comprising an unknown sentiment; and determine at least one sentiment associated with the second electronic communication using the neural network.