The Oxford English Dictionary ’s Word of the Day is the noun epistling:
Chiefly literary or humorous. Now rare.The earliest recorded use is from Thomas Nashe’s Haue with you to Saffron-Walden (1596): “Heere’s a packet of Epistling, as bigge as a Packe of Woollen cloth.” That’s some bigge correspondence.
The action or practice of writing letters; (also) epistolary matter, correspondence.
All OCA letters posts (Pinboard)