Hang on to the letter, and make it your New Year's resolution. If these are still on your CRs in January, dispute online or via fax. One of the boxes you can check with at least some of the CRAs reads something to the effect of "Creditor has agreed to delete this account".
I would not include a copy of the letter from the student loan company in my first round of disputes with the CRAs. Give yourself ammo for round 2, if needed.