It was in junk (thanks gmail)

Technically speaking, it's not so much an issue with gmail as an issue on how the email was sent by wikiful.com .

In your email client, use an allow list (white list) for the domain wikiful.com.

Since gmail does not have that feature, try the following in order (simple to more complex):

Use the "Not spam" button on a few messages found in Spam.

Add the sender to your contacts. In this case the sender is wikiful.com

Go to Settings->Filters and create a filter for that address using the "never send to spam" option.