We have Versions 5.1 on Microsoft Fax Console. We fax over to the customers it shows that they are receiving them but we have proof that they are not getting them . We went letters out by mail and we received checks from the ones the she mailed. We fax every week to the customer when they are past due invoices. They responded they never get our faxes. What is wrong? Could it be a virus protector blocking the fax or a set up wrong. Like I said it shows it goes from the inbox to the outbox but they didn't receive them

Need help solving this problem. We had the phone line checked nothing wrong with it.

Thanks