Inky now offers its own "digital signature". Digital signatures provide an additional layer of protection to ensure that the people you correspond with know it's really you, and not an impostor. When you successfully add an email account to Inky, you will see a green shield appear beside your email account. You will also see it in the header area in the upper right corner of the content pane.
You'll get the best experience by using Inky to digitally sign your mail. It will display some wordy, ugly looking errors in non-Inky clients, but it will display the message you wish to send to them. If you wish, you can add the Inky certificate (you can find instructions here).