Contrary to what the web page suggested:
subscribe-digest pgsql-general
**** The subscribe command did not succeed.
****
**** The command mode "digest" is invalid. The following command
**** modes, separated by hyphens ('-') or equals signs ('=') are valid:
**** noinform
**** nolog
**** nowelcome
**** quiet
**** rule
**** set
**** welcome
Valid commands processed: 1
0 succeeded, 0 stalled, and 1 failed.
