I believe that you are using Office 365 FOPE and trying the Global Admin Account to schedule reports.
Global Admin account using which you login to FOPE cannot be added under your organization because its been synced to a different OU named Admin Sync for some permissions to be assigned for that particular account to access FOPE.
The Email delivery from address should be an address mentioned under your organization in FOPE.
So to get rid of this I can suggest you is
1) Create a new user in Microsoft Online Portal
2) Add that user to FOPE Admin Center and then use his email address as an Email delivery from address
If you want then you can also promote this user as a Global Administrator
In order to add already promoted Global Admin under your organization we need to follow a KB Article.
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