To prevent the newsletter from going to Spam in the future I recommend adding it to a Bundle.
You can automatically add emails to a bundle based on criteria like who the email is from or keywords in the email.
- Open Inbox or the Inbox app.
- In the top left corner, tap or click the Menu Menu.
- Tap or click the label you want to bundle.
- Tap or click Settings Settings. On a phone or tablet, it's at the top right. On a computer, it's next to the label's name in the main menu.
- Under "Automatically add messages," tap or click Add.
- In the "From" field, tap or click the Down arrow Down Arrow and choose an option from the dropdown list.
- Enter a name, email address, or keyword.
- To include more criteria, tap or click And.
- Tap or click the Down arrow Down Arrow. Then choose an option from the dropdown list. You’ll see a list of emails that match your criteria.
Note: For iPhones and iPads, tap one of the options from the list that appears at the bottom of the screen. Click Save.
- Repeat steps 5–9 for other kinds of emails you want to add to your label.
Note: After you’ve set up bundles, any new emails that match the criteria you set will be bundled when they arrive. To add old emails to a bundle, you’ll need to add them manually.
For messages already in Spam, either move them to any currently existing bundle or label to get them out of the Spam label. While it isn't expressly stated in the documentation for Inbox, Inbox does use machine learning. The intention of machine learning is that Inbox learns from your actions, like moving a message out of Spam, rather than requiring you to set specific filters like you may have done in Gmail. 'Pinning' a message is also a quick way to move it out of Spam.