Mail list item not being persisted to Mailgun

I'm noticing subscibes to a mail list not actually be persisted to the mail list. I get the email that someone has subscribed, I accept the github PR. I notice in the Mailgun logs that all list members have been notified of a new comment (which of course there isn't one), because a new subscriber subscribed, but the sibscriber never ends up in the mail list.

Can you please look into this?

Subscription field here: https://binarymist.io/post/ Code for the website here: https://github.com/binarymist/BinaryMistBlog PR here: https://github.com/binarymist/BinaryMistBlog/pull/1430

Any prrogress on this @eduardoboucas ? Thanks.