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.