Literature suggests that source expertise and similarity between sender and receiver influence the impact of word of mouth on consumer's decision making. This paper investigates the impact of source expertise and similarity with both positive and negative email messages on consumers' intention to purchase a holiday. A conceptual framework developed from the literature indicates that the impact of source expertise and similarity on purchase intention is influenced by trustworthiness and that these relationships are not necessarily stable across positive and negative messages. Email scenarios, developed from focus groups, were used to manipulate the independent variables (expertise, similarity and message direction). These scenarios were then incorporated into a survey to facilitate the testing of the conceptual model using structural equation modelling. The findings show that sender similarity impacts on their purchase intention both directly and through trustworthiness. In contrast, source expertise does not impact on purchase intention through trustworthiness. Email message direction plays an important role as some relationships between variables are unique to negative eWOM, and the strength of others varies according to message direction.