procmail returning with exit code 0 even if it can't read its config file: How to prevent?

I am dealing with procmail the first time, so I apologize if the following question is stupid. Before I put procmail in production, I am doing a few basic tests. One of them yielded a totally unexpected result which makes it nearly worthless in my scenario: When procmail cannot read its configuration file, it nevertheless sets its exit code to 0 (true) when it finishes. This is catastrophic, because in my scenario, I am using procmail as an MDA which is executed from within fetchmail. If procmail can't read its configuration file, it can't process (deliver) messages as needed, but sets exit code 0 when it finishes; fetchmail interprets this as successful delivery and deletes the respective messages upstream. In summary, this leads to those messages being lost. The permissions in this scenario are quite complex (fetchmail + procmail + cyrdeliver over lmtp, fetchmail running under its own user account, procmail being suid and setgid, and so on), so it could very well happen that somebody makes a mistake with the permissions when something needs to be changed. Due to the problem described above, such mistakes likely lead to loss of messages. Therefore, I'd like to know how to make procmail to exit with failure (exit code other than 0) if it can't read its configuration file. To give an idea what this is about, please consider the following terminal session (irrelevant lines removed). Please note that the ownership / permissions in the config directory are wrong by intention, because this is my test case. root@morn /etc/fetchmail # whoami root root@morn /etc/fetchmail # dir total 52K drwx------ 2 fetchmail root 4.0K 2022-01-23 10:09 . drwxr-xr-x 123 root root 12K 2022-01-22 17:17 .. -rw------- 1 fetchmail root 2.4K 2022-01-23 10:09 fetchmailrc -rw------- 1 root mail 282 2022-01-23 02:49 procmailrc -rw-r--r-- 1 root root 110 2022-01-23 00:36 testmessage root@morn /etc/fetchmail # dir which procmail -rwsr-sr-x 1 root mail 92K 2017-11-16 23:42 /usr/bin/procmail root@morn /etc/fetchmail # cat /etc/systemd/system/pp-fetchmail.service User=fetchmail Group=mail ExecStart=/usr/bin/fetchmail -f /etc/fetchmail/fetchmailrc --pidfile /run/fetchmail/fetchmail.pid --syslog root@morn /etc/fetchmail # cat fetchmailrc poll pop3.example.com proto pop3 bad-header accept user "user1@example.com" ssl pass "supersecret" is "user1" here no rewrite mda "/usr/bin/procmail TARGET=user1 /etc/fetchmail/procmailrc" root@morn /etc/fetchmail # cat testmessage From: nobody@nowhere.com To: somebody@somewhere.com Subject: Test message This is a test message. root@morn /etc/fetchmail # sudo -u fetchmail -g mail /usr/bin/procmail /etc/fetchmail/procmailrc < testmessage && echo "procmail exited 0" procmail: Couldn't read "/etc/fetchmail/procmailrc" procmail exited 0 Of course, the last two lines are the problem. Does anybody know how to circumvent it? Of course, fixing the permissions would make it work correctly, but that is what I'm explicitly not asking for. I'd like to have a solution which is more robust in case of mistakes (mine or others').