I have a PC using Outlook and bought an iPhone 4s some months ago. I linked the iPhone with my outlook on the PC and had a few problems whereby once viewed and deleted from the iPhone they also disappeared from the PC and the ISP server. What I wanted was the emails to go to all devices and only be deleted from each device when I specifically requested it on said device. I played around with the settings asked a few questions and eventually the issue was resolved.
This month for my birthday I got an iPad. Connected it through iTunes and got most of my stuff transferred that way. However I now seem to have the old problem back.. Once an email is viewed on a device (Phone or Pad) it never arrives at my PC. I've been to all of the device settings PC, ISP server(Sky), iPhone and iPad and set them up so they never delete email from the server. I've also set the ISP to keep a copy on the server until I delete it.
All to no avail, I'm still not getting all mail to all devices..and only deleted when I do it specifically on a device, ISP server or PC.