Welcome to iMore! It depends. If you're using a POP3 email service you won't be able to view emails that have already been downloaded onto the phone because it will no longer be on the email server. A way around this would be to forward it to yourself and then download it using your iPad. For SMTP email you should be able to see the email on any device. SMTP doesn't download email and remove it from the server, it remotely accesses and syncs it.