The Outlook Mobile app only allows 1 managed email account to be added to the device  (https://docs.microsoft.com/en-gb/intune/fundamentals/end-user-mam-apps-android).

On Samsung devices it is possible to install a 2nd Outlook Mobile app so that an email account can be configured for each Outlook app. To do this you must use the Samsung Secure Folder (note: this does not work with Android Enterprise). This stores the app in a secure area of the phone completely separate from the normal apps and their data.

How to set up Secure Folder

Set up Secure Folder from the pre-installed icon

After you finish the initial setup, the Secure Folder icon appears on your Apps screen. The Secure Folder stub icon is displayed on the Apps screen or inside the Samsung Folder. If you turn off Secure Folder during the setup wizard, then the icon is not displayed.

To get started, click the Secure Folder icon.

Set up Secure Folder from device settings

On your device, follow these instructions:

1. Go to Settings > Lock screen and security > Secure Folder.
2. Tap Start.
3. Tap Sign in when asked for your Samsung Account.
4. Fill in your Samsung account credentials. Tap Sign in.
5. Select your lock type (pattern, pin or fingerprint) and tap Next.
6. Secure Folder is now set up and is created on your device.

NOTE - To open Secure Folder, tap the Secure Folder icon created on your device apps screen.

Then open the secure folder on the phone and use the “Add Apps” button.

It should then list Apps installed on phone already. Select Company Portal and Outlook.

Run Outlook. Add 2nd managed email account.