In a hybrid Exchange organization, are you trying to use a single MigrationWiz source endpoint without accounting for mailboxes that are split between on-premises and Exchange Online?

Hybrid environments place mailboxes in two distinct locations: Exchange Online in M365 and on-premises Exchange Server. Because the EWS endpoint and service account RBAC requirements differ between those locations, they require separate MigrationWiz source endpoint configurations.

For on-premises Exchange mailboxes as the source, the EWS endpoint URL must point to the on-premises Exchange CAS server external FQDN. The migration service account needs ApplicationImpersonation assigned in on-premises Exchange RBAC, not in Exchange Online, and firewall rules must allow inbound connections from MigrationWiz IP ranges to the on-premises EWS endpoint.

For Exchange Online mailboxes as the source, use the standard Exchange Online endpoint configuration, with ApplicationImpersonation scoped at the Exchange Online organization level.

If you submit a job using the Exchange Online endpoint against an on-premises mailbox, MigrationWiz queries Exchange Online for a mailbox that is not there. That comes back as an empty result, and the job closes as complete with zero items migrated, an outcome that can look identical to a permissions issue.

Have you inventoried which mailboxes are on-premises versus Exchange Online before creating separate MigrationWiz endpoint configurations for each population?

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