Attachments not received

I have a client outside our network sending me email using the same program we do (Outlook 98). I get the email fine, but attachments come across only as some weird text name (i.e. <>). I've talked them through the "how to attach a file" procedures several times and had them tell me what their email options were set to (all normal that I could see - using Rich Text), but still getting same results. Any ideas out there?