Canary allows you to include a custom signature with each outgoing message. 1) Open Canary. 2) At the upper-left corner of the screen, tap the More Actions icon. 3) In the upper-left corner of the screen, tap the Settings icon. 4) Scroll to the composing section. 5) Tap Signatures. 6) Enter a plain-text signature. (HTML is not supported at this time) 7) To use different signatures for every account, toggle ON Per Account.