Canary Mail allows you to include a custom signature with each outgoing message on your Android devices.
1. Open the application.
2. At the upper-left corner of the screen, tap the Hamburger icon.
3. In the upper-right 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)
