Check my wp_mail() code? For a lite edit flow notifications plugin. (Github)

If anyone has the time, my wp_mail() plugin isn’t working. I know the post transition hook is firing because I got an error when saving a post as pending. I fixed that. But no emails are being sent. All the email addresses involved are forwarding aliases on NearlyFreeSpeech.NET. That may be a problem?

All code on Github…

https://github.com/lukejanicke/roots-edit-flow/blob/master/roots-edit-flow.php