I have multiple POP3 email accounts which all deliver email to a single PST file. However, one of my clients recently migrated to Exchange, and so I have an Exchange account as well. For convenience in setting up meetings (he is my major client), I migrated all of my appointments (for whichever client, plus my personal ones too) to the single Exchange calendar. So I now have a sort of hybrid system where POP3 accounts deliver to the PST, while client X email and all of my appointments are done in Exchange.

However, I cannot delete the calendar in my PST file. It would appear that it is still being used, and specifically any meeting requests that I get from other clients that come in via the POP3 accounts all get posted to the PST Calendar. I would dearly love to stop it happening, and just use the one calendar and delete the old one, but I cannot see how to do it. Does anyone have any clues?

I'm happy to consider other ways of setting up the calendars/accounts, but fundamentally I want to refer to just one calendar - I don't want to have to cross refer. I also want the convenience of my client seeing when I am free/busy, plus I currently push the whole thing to my iPhone (rather than syncing, which recently gave me much grief when it stopped working properly!)