To make the act of receiving e-mail in Outlook trigger a database update, you have to be EXTREMELY careful, 'cause Windows security is set up to prevent this at all costs. Most anti-viral packages have this same goal and will stand in your way.
See, viruses come in through mail and trigger an action that runs another program. Most viral checkers with heuristic ability will take one look at that and positively go into a howler-monkey frenzy.
Further, to make this work, you have to trigger code that runs in OUTLOOK, not in Access. After all, the event in question is an Outlook event, not an Access event. So you need to look into what VBA support is provided for Outlook events.
Your alternative is to let the mail come to Outlook but just stay there until you run a "harvester" in Access that gathers up whatever has been received and processes each message, one at a time. That will be less likely to trigger an anti-viral panic attack.
If you are on WinXP, particularly on SP2, you will have a massive problem unless you alter the system security-level setting down a notch to allow code to be triggered by e-mail.