found this in a search for mail art calls; doesn't seem to have been posted previously:

2021 Worldwide Call for Mail Art

Oct 10, 2020 – Los Angeles: Artists for A Better World International is calling upon global artists to send Mail Art to AFABW Int by April 15, 2021 (World Art Day). The theme for this Mail Art project is “Honoring Artists,” in recognition of the role of artists to inspire the world through their work.

Mail Art submissions will be featured on the AFABW Int website as well as on the weekly cable television series, Our Ventura TV, and social media channels.

There’s no cost to participate.

Create and have fun.

Send us your Mail Art!

Mail Art Movement

Mail Art is a global artistic movement centered on sending small-scale artworks through the postal service.

Media commonly used in Mail Art includes postcards, paper, rubber stamps, artist-created stamps (called artistamps), photography and paint, but can also include music, sound art, poetry, or anything that can be put in an envelope and sent via global postal services, such as a collage of recycled images and objects.

Mail art is considered art once it is sent.

Mail Art 2021 Details

THEME: This Mail Art theme is “Honoring Artists.”

ELIGIBILITY: Anyone in the world may participate.

COST: NO COST (other than postage to mail your art).

CELEBRATE: This Mail Art project celebrates World Art Day.

TV LIMITATIONS: All Mail Art that reflects the theme is welcome. However, there are limitations to the quantity and presentation of Mail Art that can be shown on TV. Such limitations include no nudity, no strong language, etc. Think in terms of “family-friendly” for U.S. television.

DEADLINE: Send your Mail Art by April 15, 2021 (World Art Day) to the following address:

AFABW Int Mail Art PO Box 1872 Ventura, CA. 93002 USA

You are encouraged to sign up for the AFABW Int “Art Line” eNewsletter for updates and other art opportunities.

Mail Art Exhibition Details

• Featured Mail Art will be posted on the AFABW Int website.

• Featured Mail Art will also be posted to AFABW Int social media channels.
• Additionally, featured Mail Art will be broadcast on the weekly cable television series, Our Ventura TV, in California.