qmail-chkuser is one of the most useful qmail patches available out there. It helps reduce bandwidth usage for spam emails directed to non-existant users by rejecting them at SMTP level. Previous versions of chkuser was named chkusr, I used to use chkuser-0.6 from Bill Shupp‘s website due to its simplicity. The newer version (chkuser — notice the ‘e’) combines several other patches and provides configurable settings. Some people may like this but some (including me) may not. I use many qmail patches and prefer to keep only the patches that I use. I used chkuser for the latest qmail installation I installed and disabled other patches chkuser comes with including logging. Its logging function presented problem with stunnel. Somehow output of the log goes to stunnel instead of the log files causing problem. I looked for a fix on Google and found a similar problem including a fix. My stunnel installation doesn’t have ‘-f’ parameter as suggested by patch author, Antonio Nati, so I decided to disable logging and solved the problem.