In a method and system for generating a referencing secondary electronic mail message from a primary electronic mail message, a reference to accompanying data in the primary electronic mail message is obtained that allows reconstitution of the accompanying data from the reference. The referencing secondary electronic mail message is composed with the reference embedded therein instead of the accompanying data. Conversely, a non-referencing electronic mail message is reconstituted from a referencing electronic mail message that includes at least one reference indicative of respective accompanying data by accessing a copy of the respective accompanying data pertaining to each reference in the referencing electronic mail message. The referencing electronic mail message is augmented with the respective copy of the accompanying data relating to each reference.