Help me with libesmtp 0.8.12 please.

Hi there,
  I ran into a strange problem when using libesmtp (version 0.8.12).
when
running example/mail-file, if I pass a ipaddress instead of the hostname

of a smtp server to the -h arg, after the smtp session, the call to
auth_client_exit() will result in a "Segmentation fault" error. I've
trace into the function, and find it was cause by the  call of dlcose().

What's the problem there? Can I use IP Address instead of Hostname with
smtp_set_server()?

I use a RedHat Linux 7.2(kernel 2.4.9), with glibc-2.2.4-19.3 and
gcc-2.96-98, and have dlsym() functions supported.

Thanks in advance.