Astonishing:

-----------------------
*****@gangster:~$ dig aol.com.au mx

; <<>> DiG 9.2.1 <<>> aol.com.au mx
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 1077
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 3

;; QUESTION SECTION:
;aol.com.au.                    IN      MX

;; ANSWER SECTION:
aol.com.au.             225     IN      MX      15 mx.aol.com.au.

;; AUTHORITY SECTION:
aol.com.au.             41285   IN      NS      dns-01.ns.aol.com.
aol.com.au.             41285   IN      NS      dns-02.ns.aol.com.
-----------------------

Ok, aol.com.au have one mail exchange server. As far as I can tell, this
record only pooints to one IP address as well (not round-robin DNS as
far as I can tell). So, considering that it at least appears that they
only have one machine handling it, you'd want to to be a  really well
set up, stable, well though out installation. And no, it's not
windows.... 

-----------------------
*****@gangster:~$ telnet mx.aol.com.au 25
Trying 210.10.86.14...
Connected to 210.10.86.14.
Escape character is '^]'.
220 localhost.localdomain ESMTP Sendmail 8.11.6/8.11.6; Fri, 16 Aug 2002
10:42:09 +1000
-----------------------

localhost.localdomain?!????!?! That's the default setup for redhat if
you install it without knowing your real IP/hostname or domains and just
keep clicking "next". But surely they wouldn't have just put in a redhat
CD and ticked "install all".. Would they?

-----------------------
****@gangster:~$ curl -I http://mx.aol.com.au/
HTTP/1.1 200 OK
Date: Fri, 16 Aug 2002 00:43:52 GMT
Server: Apache/1.3.22 (Unix)  (Red-Hat/Linux) mod_ssl/2.8.5
OpenSSL/0.9.6b DAV/1.0.2 PHP/4.0.6 mod_perl/1.26
Last-Modified: Tue, 16 Jul 2002 03:23:28 GMT
ETag: "17aa94-58-3d3391b0"
Accept-Ranges: bytes
Content-Length: 88
Connection: close
Content-Type: text/html
-----------------------

Hrm... mod_ssl, openssl, webdav, PHP and mod_perl.... Yup.. That's just
about everything... 

Terrible, terrible work.