The fax came from an area code of 200 as I saw it when it was being faxed. If you fax it back, you are probably "establishing a relationship" because you contact them. Then they can legally fax you. I plan to throw it in the trash where it belongs.

Faxed their unwanted Fax right back to them. it went to a "Distant station" fax 888-247-1287

The fax I received said:

Send Us Your Unwanted Faxes
You have the right to "opt-out" from receiving future faxes.
Many people do not take the time to "opt-out" or try to improperly which results in continued unwanted faxes.
We offer our assistance for FREE!
We do not sell goods or services and we will never contact you.
Please fax your unwanted faxes to us, we will contact the sender and have your fax number permanently removed from their fax list.
The sender has thirty (30) days to comply.
Please make sure your correct fax number is on the fax you sent to us.
We need this information when we opt-out for you.
Fax your unwanted faxes to:
877-741-7368.

Received an unsolicited fax from them saying "Send us your unwanted faxes", that they will contact they sender and have them remove your fax number from their list for free. Sounds like BS, considering that I don't want THEIR unsolicited fax in the first place. I'm filing a complaint with the FCC. There are similar scams where people call you pretending to be associated with the Do-Not-Call List, who offer to help you sign up for that, for a fee.
There is no company name listed on the fax, either. Shady.