Proof of delivery changes the dynamic
When you send your appeal by USPS Certified Mail with return receipt, you get a signed record of exactly when the company received it. That starts any response clock in your contract and kills the "we never got it" defense.
Keep the green card
The return receipt goes in your case file alongside your call log. If you later file a regulator complaint, this timeline is your best friend.
Verify the address first
Appeals departments move. Confirm the mailing address on the company's website or by phone before you send — Denial Decoder's letter tool builds this verification step in.