[imp] IMP attachment as link

[nA ni sivAm]

Inside the local network, I have configured such that horde application is
directed via local ip address, say http://10.0.0.1/horde/imp/..etc

When a user is attaching a file *as a link* in a new message (IMP 4.3) , IMP
always uses the 10.0.0.1 addressing.
Obviously the link will not work when sending a mail outside the network.
However, when one replaces the 10.0.0.1 with the corresponding static ip or
the actual domain name, others can download.

Is there anyway that this link when generated uses a predefined - static ip
or domain, irrespective of how the horde application is accessed?