According to one embodiment of the present invention, a method for cross-service tagging is provided. The method includes creating connections to multiple applications, each application having multiple entities. Relationships are determined between the entities within a single application and between entities across multiple applications. A tag is associated with a selected one of the entities in a first one of the multiple applications. Entities in other applications besides the first application are identified that are related to the selected entity, based on the determined relationships. The tag is propagated across multiple applications by associating the tag with the identified entities in the other applications. According to a second embodiment of the present invention, a method for inferring tags suggestions is provided. This method includes analyzing email messages to create keywords from text analysis, from bringing content and tags from other email messages or directory applications. Tags suggestions from the various sources are merged and weighed according to an algorithm.