Version:            (using KDE KDE 3.3.1)
Installed from:    RedHat RPMs
OS:                Linux

When running Kmail with "local mail" and "Procmail lockfile", you get a lot of:
lockfile: Try praying, giving up on "/var/spool/mail/luna.lock"
AFAICS, Kmail doesn't use the "lockfile" utility (that comes with procmail) as intended. lockfile is installed setgid "mail", and when you run it with the -ml/-mu switches, it creates/removes .lock files in /var/spool/mail for the user running it, even when the user don't have write permissions in the /var/spool/mail directory (which is the default). However, Kmail runs lockfile with a named .lock file on the command line, and in that case, lockfile drops it's setgid privs before trying to create the .lock file, and thus failes. My suggestion for Kmail is to use the intended -ml/-mu switches instead of a named .lock file. Here's my hack to do that:

diff -u kdepim-3.3.1.orig/kmail/kmfoldermbox.cpp kdepim-3.3.1/kmail/kmfoldermbox.cpp
--- kdepim-3.3.1.orig/kmail/kmfoldermbox.cpp	2004-08-05 21:26:53.000000000 +0200
+++ kdepim-3.3.1/kmail/kmfoldermbox.cpp	2005-04-22 08:02:54.000000000 +0200
@@ -337,12 +337,13 @@
       break;
 
     case procmail_lockfile:
-      cmd_str = "lockfile -l20 -r5 ";
+      cmd_str = "lockfile -l20 -r5 -ml";
+      /*
       if (!mProcmailLockFileName.isEmpty())
         cmd_str += QFile::encodeName(KProcess::quote(mProcmailLockFileName));
       else
         cmd_str += QFile::encodeName(KProcess::quote(location() + ".lock"));
-
+      */
       rc = system( cmd_str.data() );
       if( rc != 0 )
       {
@@ -466,11 +467,13 @@
       break;
 
     case procmail_lockfile:
-      cmd_str = "rm -f ";
+      cmd_str = "lockfile -mu";
+      /*
       if (!mProcmailLockFileName.isEmpty())
         cmd_str += QFile::encodeName(KProcess::quote(mProcmailLockFileName));
       else
         cmd_str += QFile::encodeName(KProcess::quote(location() + ".lock"));
+      */
 
       rc = system( cmd_str.data() );
       if( mIndexStream )