3. The network device of claim 1 , wherein the at least one keyword is identified based on employing a sequence of heuristics, including: replacing a relative reference with an explicit reference within the relevant sentence; replacing a pronoun with a noun for which the pronoun refers within the relevant sentence; removing information determined to be sensitive or objectionable from within the relevant sentence; and selectively removing stop words within the relevant sentence, such that at least one resulting word is identified as the at least one keyword.
1. A network device, comprising: a transceiver to send and receive data over a network; and a processor that is operative on the received data to perform actions, including: receiving a message having at least one attachment; using a machine learning model to select at least one sentence from within the message to be relevant to the at least one attachment based on a set of predefined sentence level features; identifying from within the relevant sentence at least one keyword determined to be further relevant to the at least one attachment; and associating the at least one keyword to the at least one attachment, such that the association is useable for at least one of indexing or searching of the at least one attachment.