I'm still not sure if my experiences with postfix on Freedombox are related. However, no one has told me that my last message was noise. So, I will just add that the same thing has happened again: postfix's main.cf was overwritten somehow and didn't include my domainname in it anymore.
The result was valid incoming mail to my domain was being rejected with the error code 454 4.7.1 and the message Relay access denied. "ls -lAF" dated main.cf at November 11. According to the apt logs, freedombox, freedombox-doc-en and freedombox-doc-es were updated on November 11.
