Include PGP Key Setting

New eM Client user here - and generally new to PGP as well. My keypair is successfully included in both the desktop and mobile versions of the application. In the Signing and Encryption section of the settings, I have “Include certificates/keys in outgoing message” on, again, both desktop and mobile. However, it eM Client does not appear to automatically include my public key in unsigned outgoing messages. Am I misunderstanding what that setting is supposed to do, or is something wrong somewhere? I thought it would include my public key by default. Much appreciated.