qmailadmin-logger.patch for version 1.2.9, 1.2.10 and 1.2.11 written by Metin KAYA [metin@enderunix.org], Istanbul/TURKIYE
Please create /var/log/qmailadmin.log file and change its owner:
# touch /var/log/qmailadmin.log && chown vpopmail:vchkpw /var/log/qmailadmin.log
--- user.c	2007-08-12 13:09:41.000000000 +0300
+++ user_enderunix.c	2007-08-12 13:10:41.000000000 +0300
@@ -24,6 +24,7 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <sys/time.h>
 #include <unistd.h>
 #include <pwd.h>
 #include <dirent.h>
@@ -64,6 +65,35 @@
 #define HOOK_LISTDELUSER "dellistuser"
 #endif
+static void
+log_patch(char *msg)
+{
+    FILE *fp = NULL;
+    if ((fp = fopen("/var/log/qmailadmin.log", "a")) == NULL) {
+	fprintf(stderr, "File: %s -Line: %d: %s.\n", __FILE__, __LINE__, strerror(errno));
+	exit(-1);
+    }
+
+    const char *ip_addr = getenv("REMOTE_ADDR");
+    if (!ip_addr)
+        ip_addr = "127.0.0.1";
+
+    time_t tv;
+    struct tm tm;
+    char time_buf[64];
+
+    time(&tv);
+    localtime_r(&tv, &tm);
+    strftime(time_buf, sizeof(time_buf) - 2, "%d/%m/%Y %H:%M:%S", &tm);
+
+    fprintf(fp, "%s: %s@%s logged in from IP: %s. Action: %s\n", time_buf, Username, Domain, ip_addr, msg);
+
+    if (fclose(fp) != 0) {
+        fprintf(stderr, "File: %s -Line: %d: %s.\n", __FILE__, __LINE__, strerror(errno));
+        exit(-1);
+    }
+}
+
 void show_users(char *Username, char *Domain, time_t Mytime)
 {
   if (MaxPopAccounts == 0) return;
@@ -506,6 +536,11 @@
     snprinth (StatusMessage, sizeof(StatusMessage), "%s %H@%H (%H) %s",
       html_text[2], Newu, Domain, Gecos,
       html_text[119]);
+      
+      char log_buf[3 * MAX_BUFF];
+      memset(log_buf, 0x0, sizeof(log_buf));
+      snprintf(log_buf, sizeof(log_buf) - 2, "user added [%s@%s]", Newu, Domain);
+      log_patch(log_buf);
   } else {
     /* otherwise, report error */
@@ -590,6 +625,12 @@
 {
  static char forward[200] = "";
  static char forwardto[200] = "";
+ char log_buf[4 * MAX_BUFF];
+ char tmp_buf[MAX_BUFF];
+
+ memset(log_buf, 0x0, sizeof(log_buf));
+ memset(tmp_buf, 0x0, sizeof(tmp_buf));
+ snprintf(log_buf, sizeof(log_buf) - 2, "user deleted [%s@%s].", ActionUser, Domain);
   if ( AdminType!=DOMAIN_ADMIN ) {
     snprintf (StatusMessage, sizeof(StatusMessage), "%s", html_text[142]);
@@ -612,8 +653,15 @@
     if(adddotqmail_shared(ActionUser, forwardto, -1)!=0) {
        snprintf (StatusMessage, sizeof(StatusMessage), html_text[315], forwardto);
     }
+
+    if (strlen(forwardto) > 5) {
+    	snprintf(tmp_buf, sizeof(tmp_buf) - 2, " And his/her mails were forwarded to %s.", forwardto);
+   	strncat(log_buf, tmp_buf, sizeof(log_buf) - 2);
+    }
+
   } 
+  log_patch(log_buf);
   call_hooks(HOOK_DELUSER, ActionUser, Domain, forwardto, "");
   show_users(Username, Domain, Mytime);
 }
@@ -814,6 +862,11 @@
       /* snprinth (StatusMessage, sizeof(StatusMessage), "%s %H@%H.", html_text[139], 
 ActionUser, Domain ); */
       strcpy (StatusMessage, html_text[139]);
+
+      char log_buf[3 * MAX_BUFF];
+      memset(log_buf, 0x0, sizeof(log_buf));
+      snprintf(log_buf, sizeof(log_buf) - 2, "password changed for %s@%s", ActionUser, Domain);
+      log_patch(log_buf);
     }
   }
@@ -842,6 +895,10 @@
         snprintf (StatusMessage, sizeof(StatusMessage), "%s", html_text[307]);
       } else { 
         snprintf (StatusMessage, sizeof(StatusMessage), html_text[309], qconvert);
+        char log_buf[3 * MAX_BUFF];
+        memset(log_buf, 0x0, sizeof(log_buf));
+        snprintf(log_buf, sizeof(log_buf) - 2, "quota changed to %s MB for %s@%s", Quota, ActionUser, Domain);
+        log_patch(log_buf);
       }
     } else {
       snprintf (StatusMessage, sizeof(StatusMessage), "%s", html_text[307]);
@@ -1178,4 +1235,3 @@
   }
 }
-