Subseries is made up of envelopes, collected between 1978 and 2018. While it is uncertain why envelopes were separated and maintained as a separate series, although it is likely some were used for in various shows as examples of Mail Art. Envelopes played a large part in many mail art shows and often the subject of shows themselves. They are important mediums in the proliferation of mail art in all periods.

Envelopes are often heavily decorated with artistamps, rubber stamps, paintings and drawings, and other materials.