Subscribe to blog posts does not work in EF blog

[Inspector-Butters]

Describe the bug

When you sign up to be a subscriber to the EF blog posts (https://blog.ethereum.org/), it tells you:

Thank you for signing up! Check your inbox to confirm your subscription.

but sends no email.

To reproduce

1. Go to https://blog.ethereum.org/
2. Scroll down to the bottom of the page to see "Subscribe to Protocol Announcements"
3. Enter your email in the field and click on "Sign up"
4. See the message "Thank you for signing up! Check your inbox to confirm your subscription."
5. See that no email is sent to you, hence, error.

Expected behavior

The expected behavior is to receive the email to be able to confirm the subscription.