1. A computer-executed method for filtering outbound content via inference detection, the method comprising: identifying previously sent content associated with a common first destination identifier; extracting a set of keywords from the identified previously sent content; issuing a set of web search queries that each includes one or more of the extracted keywords to obtain a set of search results; extracting a set of candidate keywords from the set of search results; performing inference detection using the set of search results for the extracted keywords; determining, from the set of candidate keywords, a set of expected-content keywords which are determined to be representative of the previously sent content based on the inference detection; responsive to receiving a piece of outbound content, determining whether the outbound content is proper, which involves performing one of: determining that the outbound content is associated with the first destination identifier, and the number of expected-content keywords present in the outbound content is below a first predetermined threshold; and determining that the outbound content is not associated with the first destination identifier, and the number of expected-content keywords present in the outbound content is above a second predetermined threshold; and; and responsive to the outbound content being improper, displaying the destination identifier for the outbound content and at least one expected-content keyword present in the outbound content.