As I stated:
+With a POP account, deleting a message from the account's Inbox mailbox does not affect the message remaining on the server unless you have remove messages from the server when moved from Inbox. The message should be available to download with Outlook after doing so, and vice-versa - unless you have the POP account settings with Outlook set to remove messages from the server after being downloaded by Outlook. Messages are not kept synchronized with the server with a POP account.+
I had a blackberry and I could delete emails from it and they stayed on the server so I'm not sure why the Iphone won't do it.
A Blackberry is not an iPhone. Different from a Blackberry, the iPhone's Mail app communicates direct with the incoming mail server for an email account - no different from accessing an email account with an email client on your computer such as with Outlook, not through a 3rd party dedicated email delivery service that is located in Canada which includes options that are not available with an email client that communicates direct with the incoming mail server as with every other email client.