To manage mailboxes in Exchange Online, it is recommended to assign the Exchange administrator role to the account used to register your Microsoft 365 tenant in Adaxes.
In case of Exchange on-premises, you need to grant corresponding permissions to the account whose credentials are specified for a managed domain. For information on how to check/change the account, have a look at the following help article: https://www.adaxes.com/help/ChangeManagedDomainServiceAccount. It is recommended to assign the account to the Organization Management role group. It provides administrative access to an entire Exchange organization and can perform almost any task.
If, for some reason, you do not want to provide the account administrative access to your Exchange organization, you need to assign the account to the following role groups in Exchange:
For more details, see Understanding Management Roles.