If you are unable to find the sign out or log out option on Yahoo email app, go to Settings, head over to Mail, Contacts, Calendars and then turn off mail sync option.
The email will be moved to your Inbox and Yahoo shouldn't filter future correspondences from that sender.
If it was, you need to open the email in your browser and click the Not Spam button at the bottom of your window. If you are still unable to receive email, please check your Bulk Mail folder to see if the email was filtered there. It appears that the issue is caused due to some incorrect permission settings or some network settings. If you could not print emails using default printer then there might be a chance that the account through which you are logged in doesn't have much permission to perform these changes.
