Though I'm not aware of a standard report for this, you can query table NAST with SE16 or SE16N. In your case, use selection criteria:
- Application = EF (purchasing)
- Transmission medium = 2 (fax)
- Processing status = 1 (successful)
You may need to pick a message type (typically NEU), depending on what sort of documents you send to the vendor.
For regular use by client personnel, you can make a permanent query using transaction SQVI, which you can assign to a report name.
I hope this helps.
- Jeff