file should be set up last, because that's the one that tells Exim there is a
message to be delivered, so we create its new link last and remove its old link
first. Programs that look at the alternate directories should follow the same
-rule of waiting for a -H file before doing anything. When moving messsages off
+rule of waiting for a -H file before doing anything. When moving messages off
the mail spool, the -D file should be open and locked at the time, thus keeping
Exim's hands off. */