We have recently encountered an issue during the initial set up of Outlook for mobile application on iPhones/iPads. Setting up the email account resulted in errors due to low space on the device.
We've seen two different cases where one device gave a generic error of ‘Login Failed’ while a couple of others simply jumped back to the start of the setup process without warning. In both cases, an error message doesn’t come up to point to the actual problem of having a lack of free space.
So if you’re having trouble setting up your email in the Outlook app on smart devices, it could be because your device doesn’t have enough free space. Try freeing up some space and try again.
So far we've only seen this issue occur on Apple devices, but it may occur on other devices. If you encounter this issue on another mobile device, we recommend following the same steps or talking to your IT support technician for further help.