Hackernewsletter is failing both SPF and DKIM checks

[cdman]

See for example:

This means that the emails are frequently ending up in the spam folder. Here is an article from mailchimp that has some info on setting up SPF/DKIM correctly: https://mailchimp.com/help/set-up-email-domain-authentication/. Also, I'm happy to provide more information if it would be helpful.