What exactly do you mean with "Outlook account"? MS Outlook is a program (part of the MS Office suite), not an e-mail provider.
This post is from earlier in the year, but it might help you:
We also did a review of the Outlook.com app for Android today, which might have some pointers for you:
CNET How To
Hoarding photos on your phone?
Those picture are hogging memory and could be slowing down your phone.