You have a couple of options.
If it's an exchange account everyone seems to prefer Touchdown as a email app on the Droids. If it's just personal Outlook type account you can use K-9 or MailDroid to sync with Outlook through Google. Both of these apps are very good and they can be set to poll the Outlook account(s) at a frequency of your choice.
The native email for Pop3 accounts is terrible and no one uses it.
An option that I just started using a few weeks is to have all emails sent to my Gmail app on the Droid. You have to set it up on Google's website/your gmail account. Google will then check your Outlook accounts at a frequency based on each account's activity. If there is a lot of email activity, it will be polled fast (1-3 minutes). If there isn't much activity, polling may be as slow as every 5 minutes. Either way, you save on battery by not having an email app wake up and poll the outlook accounts every few (1-15) minutes.
Good luck.