Mike Hearn, a Google engineer who became an early Bitcoin contributor, exchanged a series of emails with Satoshi Nakamoto between 2009 and April 2011. Hearn had first contacted Satoshi after reading the Bitcoin white paper and becoming interested in the project.
In their correspondence, Satoshi discussed technical aspects of Bitcoin’s future, including how the system could scale, how simplified payment verification (SPV) clients would work, and how he envisioned the evolution of mining from CPUs to more specialized hardware.
On April 20, 2011, Hearn asked Satoshi directly:
Quote from: Mike Hearn on April 20, 2011, 1:55:00 PM UTC
“…are you planning on rejoining the community at some point (eg for code reviews), or is your plan to permanently step back from the limelight?”
Three days later, Satoshi replied:
Quote from: Satoshi Nakamoto on April 23, 2011, 3:40:00 PM UTC“I’ve moved on to other things. It’s in good hands with Gavin and everyone.”
It was among the last known private messages from Satoshi before he went silent.
Hearn published the full correspondence in August 2017.
This April 23, 2011 exchange is treated as the upstream record by the Satoshi final-known-email entry, which pairs the April 23 Hearn farewell with the April 26 Andresen alert-key transfer as the documented ‘farewell pair’ that closes Satoshi’s public correspondence.