package: postfix version: 2.3.7-3 Postfix 2.3.7 seems to have dropped the file RELEASE_NOTES_2.2. This is necessary for people upgrading from Sarge to understand what has chanegd since Sarge's version 2.1.5. I believe this file was last shipped with version 2.3.6.
The file RELEASE_NOTES.gz even includes a mention of it: "Critical notes -------------- See RELEASE_NOTES_2.2 if you upgrade from Postfix 2.1 or earlier." -- Pete Boyd