Colonel W. Preston Corderman was responsible for censoring all mail on the home front that was addressed to foreign lands or was mailed from foreign lands.
"Colonel Corderman himself can break down any codes in any language... when the war broke out the Army loaned him to the post office as chief code cracker. The colonel says it's easy to tell by the tone of a letter whether it conceals some hidden meaning."
Click here to read about censoring the mail during W.W. I.