Add Postfix example, use recommended queue id.

docs/INSTALL

@@ -113,11 +113,15 @@ Configuring Whups
    appropriate addresses. This script takes a number of arguments; see the
    script for more details. A typical setup might be::
 
-      bugs |/usr/bin/whups-mail-filter --queue-name=Bugs
+      bugs |/usr/bin/whups-mail-filter --queue-id=1
+
+   For Postfix:
+
+      bugs: |"/usr/bin/whups-mail-filter --queue-id=1"
 
    This will take in mail to the ``bugs`` address at your domain, and create
-   new tickets in the ``Bugs`` queue, with the default type, state and priority
-   of this queue. If an email references an existing ticket (ticket numbers are
+   new tickets in the queue 1, with the default type, state and priority of
+   this queue. If an email references an existing ticket (ticket numbers are
    recognized in the subject line) it will be updated instead.
 
    If not installing Whups through PEAR of if PEAR's ``bin_dir`` configuration