The following are instructions on how to delete your Office 365 Exchange (Outlook) account from the iOS Native mail client (the mail app on iPhone/iPad).
If you need to add your account again, try our article: Setting up IOS Mail App for Office 365 Exchange
If you still have questions or need additional assistance, please contact the ITS Service Desk. You can call us at (858) 246-4357, email us at support@ucsd.edu, or submit a ticket at support.ucsd.edu.