I have had some trouble with Portfolio - here's my history with them:
Sent DV on 10/08/07 via CMRRR
Received response on 11/01/07 - response was an Affidavit of Ownership and Sale of Claim
Sent a follow-up DV on 11/02/07 via CMRRR
Received response on 11/18/07 - debt was validated, but CA was not licensed as a collection agency in Arizona
Sent complaints to the AZ Dept of Financial Institutions, AZ Attorney General, VA Attorney General, and FTC (cc'd Portfolio via CMRRR) on 11/30/07
Waiting for AZDFI response - Portfolio continues to update the collection on my credit reports monthly.
10/22/07 (FICO) EQ 544 EX 520 TU 518
03/04/08 (FICO) EQ 606 EX 599 TU 601
04/24/08 (FICO) EQ 600 EX 580 TU 608
06/02/15 (FICO) EQ 578 EX 561 TU 589