It’s unlikely to come from iCloud. One of the Office apps, or OneDrive, or some other app that gets signed into with that Outlook email account is possible. Even that seems unlikely. I have an Office 365 account and several Microsoft apps. I have no problems using Outlook with an unrelated email address. The only thing I use Outlook for is to monitor our club’s email account; keeping it separate from my personal accounts. Did you ever try deleting the account from Outlook as per Johanna’s instructions? Also, while data for an app is supposed to be deleted when an app is deleted, it’s not always immediate. Restarting the iPad and/or waiting a while before re-installing the app might help. That aside, if you are using an iPad with a previous owner’s iCloud and Apple account, it’s very difficult to un-associate it from that account and it’s data. Even though it may mean having to purchase a few apps again, it’s better to start fresh with your own account. Also, it’s against Apple’s user agreement, so you could be forgoing any support you could get from Apple in case of serious issues with the software or hardware. One more thing you can check. It’s possible your iPad was set up by a school or business. If so it may have a profile installed. You can check to see if there is a profile installed under Settings > General > Profile. If there is no profile option, then no profile is installed. If there is, it may or may not be possible to delete it. Profiles can be locked by the organization that installed them. If that’s the case, your only option is to go back to that organization and have them remove the profile.