[haroldz]

I didn't say put the number on the internet. Look at the next fax you see. There is supposed to be a telephone number identifying the sender. What I am saying is to check the sender's telephone records for the recipients from that sender's number. Obviously easier said than done.

[ASA Vet]

There is supposed to be a telephone number identifying the sender

That information is programmed in by the owner/user of the FAX machine.
I can program my FAX with any phone number and name, or none at all.