Gary Fischman asked something that reformatted to read,
| Why, in some recipes, do I get a "USER: Undefined variable" error? Is
| procmail or formail expecting that to be defined? If so, what should it be
| set to? None of the recipes fail, they just dump an error into the log file.
Some versions of procmail predefine USER=$LOGNAME; some do not. Perhaps you
are using one of the latter and have a recipe that refers to $USER or which
calls a program or script that references $USER.
What happens if you put
:0 # if $USER is unset, set it equal to $LOGNAME
* $ ${USER+!}
{ USER = $LOGNAME }
near the beginning of your .procmailrc, or if you replace $USER in the recipe
[or in the script it calls] with ${USER-$LOGNAME} instead?