fax server question - tg

We have purchased a new internal modem and installed it in a Windows 2003

server, and installed the fax services. Everything seems to be working well

but we are not able to fax to most of the numbers we have tried. We have 3

local faxes. We can successfully fax to 1 of the 3. One of the others gives

an error "there was no answer" at the other end. The other one keeps saying

"busy". We are able to successfully fax to one fax number. We have done

this 3 times with no problems. Our modem is a nexxtech brand modem. We

have played with the settings and we have not been able to see any changes.

Can someone please help. thanks already, tom