How to remove the default K-9 Signature "Sent from my Andorid device with K-9 Mail. Please excuse my brevity." 1. Press and hold on the account you want to change the signature on in K-9 Mail. 2. An options menu will appear. 3. Click Account Settings > Sending Mail > Composition Defaults 4. Scroll down to Use Signature and uncheck the box to remove the signature or type in a new signature.