If you run Hybrid Migration Wizard and you noticed that Migrated users from Exchange On-Premises to O365 are not redirected to O365 Owa page then you will have to go through the following to check if there’s an issue and fix it.
In Normal cases, This is done automatically upon running the HCW (Hybrid configuration wizard) but in some cases it might not be found. And therefore when migrated user try to login using the local Exchange OWA page the user is not redirected to O365 OWA and get’s an error.
In order to make sure that redirection is the problem, open Exchange Management PowerShell and run the below command see for ur self if the “TargetOWAURL” is set.
Below in this screen shot, the value for targetowaURL is not set, so we’ll have to set it as in the snapshot after that.
The targetowaURL will point to the OWA of the tenant Url.
The Target URL must be like in the following snapshot
To resolve this case, we’ll have to run the cmdlet
Set-OrganizationRelationship “On Premises to Exchange Online Organization Relationship” -TargetOwaURL:http://outlook.com/owa/domain.onmicrosoft.com