Does anyone know what the Navy format for writing a thank-you letter is? I've searched the SECNAVINST 5216.5D, but can't find a format. It only gives tips on how to write the letter. I am trying to write a few thank you letters to some of my former CO's who helped me out recently. Should I just use standard letter format without SSIC/Code/Serial/Via and Encl. Thanks in advance for any help.