As a ham radio nerd, packet bulletin board systems should really make a comeback. They fell apart as the internet came about, but in an effort to re-invigorate the now-unused spectrum and hardware TNCs[1] all over the place, APRS[2] was created, which has this nifty feature[3]. We also have a type of email system called Winlink[4] (which runs using the ARDOP protocol[5] or VARA[6] replacing Winmor[7] and Pactor[8]).

[1]https://en.wikipedia.org/wiki/Terminal_node_controller

[2]https://en.wikipedia.org/wiki/Automatic_Packet_Reporting_Sys...

[3]https://aprs.fi/

[4]https://www.winlink.org/

[5]https://www.winlink.org/content/ardop_overview

[6]https://rosmodem.wordpress.com/

[7]https://en.wikipedia.org/wiki/Winmor

[8]https://en.wikipedia.org/wiki/PACTOR