How to add the social icon “Mail” ?

Hi there,
Thanks for this great plugin!
I’m trying to add a “mail” social icon for authors, but I can’t find how to do this.
In the settings page of Simple Author box, all available icons seem to be shown, including Mail between Snapchat and Meetup.
But within the page of an author, where I can try to add social icons, Mail has disappeared…
How can I do this ?
Thanks for your help
Aurélien

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