[Exim] long pause when coming in from localhost

so what might be causing the loooong pause

    % telnet localhost 25
    Trying 127.0.0.1...
    Connected to localhost.
    Escape character is '^]'.
    <*** very long pause, about thirty seconds ***>
    220 barre.foux.edu ESMTP Exim 4.04 Wed, 22 May 2002 11:07:45 -0700
    quit
    221 barre.foux.edu closing connection
    Connection closed by foreign host.

i don't get it to all other hosts, just some. i don't get it from
another host to this host.

same on another exim4 host.

dns for the hostname, the in-addr.arpa for the ip address,
localhost, 1.0.0.127.in-addr.arpa, etc. are all fine.

randy