Elm is configured to only do fcntl() locking. It should be built to also do .lock since you can't be sure that everything else dealing with mailboxes understands fcntl() and only fcntl().
Since Red Hat 5.2, all mail user agents do fcntl locking *only*. If you wish to run elm with, for example, NFS mounted partions with dot locking, you will have to revert the change and recompile the package.
The idea that everything does fcntl only is fine, but wrong. Run procmail -v, for example, and you'll see that it does both .lock and fcntl. My concern isn't that things work 'out of the box', my concern is that some one installs some other package that ONLY does .lock and ends up with a conflict with elm.
Um, I don't disagree, I only provide information :-) The other package, not elm, should be fixed to do *only* fcnt;l locking.