Managing contact groups entails receiving email header information for electronic messages sent during a certain period of time. Each header includes unique identifiers for the sender and each recipient. The set of these unique identifiers from each header forms a de facto group. For each group, the process computes a usage value based on the number of distinct messages corresponding to the group. The process also identifies a set of saved groups, where each saved group is a set of unique identifiers of people, and each saved group has a usage value. The usage value is 0 when the saved group does not equal any de facto group. The process compares the de facto groups and their associated usage values to the saved groups and their associated usage values, and provides a recommendation to modify the set of saved groups based on the comparisons.