Sounds like a routing problem to me. It MAY be caused by the fact that the
name that is returned from the DNS when it tries to find the webmail page is
being resolved to an outside address.
A few things to ask and consider:
Can you specify the local webmail address as a "numbered dot" address (ie.
192.168.10.4 or whatever) and get it to work? If yes, then it is most likely
a DNS error problem. If no, then I would next look at your subnet mask
value. If that dot address also tries to resolve outside, then your G5
thinks that the address is not part of your local network, and automatically
hands the request to the gateway for routing outside. How your gateway
address handles it is also at question, since it too should recognize it as
an inside address. However, some gateways do not contain routes back inside
the local network, assuming that the requester has already tired that
address.
Is the "numbered dot" address in the same network as your machine? Similar
to above, but it might reside in a different local network, in which case a
route from your machine to the webmail address, or a route back is
incorrect. For example, you machine may see the webmail, but the returned
info is being routed incorrectly. This could be a NAT error (if you are a
natted address), a router error, or a sub net mask error on the webmail
machine as well as yours.
Assuming the dot address work but the name does not:
Have you entered your DNS info by hand, or does your DHCP service provide
those addresses? If provided, then an entry in the local DNS server is
needed to point properly to the local web mail address. As a test, go into
the Terminal program, and ping the webmail address by "dot address", and
then by name address. See what is returned in each case for the actual
pinged address, and if you get a response in either case.
If you are entering your DNS entries by hand (into the Network System
Preference), then they may be pointing to external servers that have no idea
where your local webmail page is.
Hope this help, or supply more info and results.
-Owen Rubin-