SBS Dials fax number multiple times

One of our customers has SBS 4.5 and is using the fax client. Most of there faxes are sent as a braodcast to about 30 people at a time. They enter the fax numbers with Outlook 2000 and then send the fax to the fax client. SBS will then dial the numbers and send the fax. The problem is that SBS can’t determine if the recipient has gotten the fax. It will send the fax multiple times to the same number throughout all the numbers in the list. It will send up to 5 faxes to the same number. Any help on this would be greatly appreciated.