Outlook working with Exchange and POP3 emails

I have a Dell laptop running Windows 7 Pro #32. It was originally a home-only PC but it now gets used at work on a domain. I am running Outlook 2007 originally just for POP3 private email. At work we have Microsoft Exchange Server and Outlook now picks up both sets of email and they both seem to run OK side by side within the same version of Outlook. The issue I have is that the POP3 emails are private and Exchange emails are work. This arrangement seemed fine and I assumed they would remain separate. That is until I setup my new smartphone to download Exchange (work) emails. This worked fine and downloaded work (Exchange) emails but it also downloaded my private POP3 emails which leads me to think that actually ALL my emails are now sat on the work server. This can't be allowed to happen.

Would really appreciate some input on whether this assumption is correct. If it is, is there a way to separate them out in the same version of Outlook and also where on the server will copies of my private be kept as I'd like to remove them?

Perhaps this will help: Not all email is created equal: an introduction to POP3, IMAP4 and MAPI | mail2web.com Blog (More links are at the bottom of that page.)

Just because you change the method of access doesn't change the location of emails which are on the server of the email service providers (the server names on the account tab of the properties for each email account). If you have been keeping work and personal email separate, they were separate because the email service providers are different. For example, it's possibe for someone to have 10 separate email accounts with 10 different email service providers located in 10 different states or countries. That person would then install 10 accounts in their one Outlook program, or if they have 2 devices, then install the accounts on either or both devices. Just be careful to use the appropriate type of service (pop3, smtp, imap, or mapi) depending on the features you want for each account.