To setup dbmail-imapd to run under xinetd you need to the following:

On CentOS 4.3: Create file: /etc/xinetd.d/dbmail-imapd File contents should look like:

  service imap
  {
      socket_type     = stream
      wait            = no
      user            = root
      server          = /usr/local/sbin/dbmail-imapd
      protocol        = tcp
      server_args     = -n
      log_on_failure  += USERID
      disable         = no
  }

Modify the path to the server as needed.

Thats it!.