How do I get mail to behave the same way on iPad 3 and iPhone 5 (both running iOS 7)?

I have a POP email account through my local cable company (Midcontinent Communications). I have several iPads (2 and 3) and an iPhone 5. The iPad 2 is running an older version of iOS. The iPad 3 and iPhone 5 are both running iOS 7. I am trying to figure out how to bet the mailboxes for my email account to behave the same way.

When I open an email on iPad 2, iPad 3 shows that I already read the email. The iPhone does not. The email shows up as unread. If I delete an email from iPad 2, it automatically deletes it from iPad 3. This behavior does not follow through on the iPhone (the email remains undeleted on iPhone). If I delete an email from iPhone, it still remains on iPad 2 and 3.

I have gone to the advanced settings for the POP account on all devices and they are set up exactly the same. My local cable company says this is just a quirk with POP accounts. Anyone else have this problem? Did you find a resolution?

On the iPhone, I went to advances settings>Incoming settings>Delete from Server - I checked , "when removed from inbox." That did not work.

Thanks.