1. A computer program product to control access to categorized messages, the computer program product comprising: a non-transitory tangible computer readable storage medium, said tangible computer readable storage medium comprising computer readable program code embodied therewith, said computer readable program code comprising program instructions that, when executed, cause a processor to: establish, based on a number of electronic messages associated with a category, a message objective, wherein the message objective: comprises a set of rules to determine how an electronic message is shared; informs user association, message association, and message access rules for each of multiple categories; comprises an allow more objective to allow grouping of electronic messages without additional input from a message originator; comprises a share objective to allow the electronic message to be shared with users in addition to the message originator and a message recipient; and wherein an electronic message comprises a categories field and a message objectives field; receive a change to the message objective; categorize the electronic message into the multiple categories according to the message objective, wherein each category is associated with multiple electronic messages; group the electronic message with other electronic messages in the multiple categories based on semantically similar message content; determine, based on the message objective a number of users allowed access to the electronic message; remove a first user from the number of users allowed access to the electronic message based on the first user having not accessed the electronic message within a specified amount of time; add a second user to the number of users allowed access to the electronic message by receiving a request from the second user registering interest in a category; and allow the number of users to access the electronic message according to the message objective.