Comcast/Xfinity differs from many email providers in that it doesn't have a "whitelist" function. Instead, if you find emails in your spam folder that should not be there, mark them as "not spam".
In XFINITY Connect, open the Spam folder from the left navigation pane.
Check the box next to the message(s) that is not spam.
Click the Not Spam button at the top of the page.
either of these symbols:
The email will be moved back to your inbox.
Note: You can also right-click on the email in the Spam folder and select Not Spam. If you still have a problem with emails going to your spam folder, contact Comcast's Security Assurance group at 1-888-565-4329 and ask if there is a blocking issue with the sender's domain (rainbowplantlife.com).