If an email should no longer be included in a box, you can remove it from the email thread or while viewing the box timeline. Removing an email from a box does not delete the email from your inbox.
Remove from a box while viewing the email
Boxed emails have a label indicating which pipeline and stage the email is in.
Click the x on the label to remove the email from that box. This will not delete the box nor the email from the recipient's inbox.
Remove an email from the box timeline
While viewing the box, locate the email you want to remove and click the trash can icon in the email preview.