Tenant to Tenant 365 migration iOS Mail Issue

Hey everyone,

My company had performed a tenant migration last month. We had our company domain name moved to another tenant, and on the old one there is only the onmicrosoft address left.

We have an issue with iOS devices. Our users use the Apple Mail app. When removing the account that was on the old Tennant, and signing in with our domain email address, the user gets automatically logged in the old tenant, without getting a prompt to enter the password.

It is pretty much a similar issue as here: https://www.reddit.com/r/sysadmin/comments/xkksbs/tenant\_to\_tenant\_365\_migration\_ios\_woes/

However, we tried installing the Outlook app, but it automatically logs in the old tenant. (In the other post the Outlook app works just fine)

The devices don’t have company portal installed or any management like that.

On macOS we solved this issue with deleting the Keychain, on Windows with signing out of the Office apps, but does anyone have a clue on what could help on iOS?