From the DoDMERB website
https://dodmerb.tricare.osd.mil/FAQs.aspx#num10q
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You may fax documents pertaining to your medical status to DoDMERB.
We do ask however, if the total number of pages exceeds 15, that you mail those instead of faxing. DoDMERB has limited ability to receive faxes and faxes exceeding 15 pages could delay our ability to process your documents as quickly as possible.
Please note: If you fax documentation to DoDMERB, you DO NOT need to mail the same document(s). Our fax number is: 719-333-3578. Our mailing address is: DoDMERB, 8034 Edgerton Drive, Suite 132, United States Air Force Academy, CO 80840-2200. DoDMERB has the capability to receive all types of mail deliveries, (i.e., US Postal Service, FedEx, UPS, etc.).