Examples of the present disclosure describe systems and methods for migrating mailbox identities. In aspects, a system may receive one or more requests to perform tasks for migrating identities of a plurality of mailboxes included in a security group created at a source tenant to a plurality of mail users created at a target tenant that correspond to the plurality of mailboxes. Based on the one or more requests, the system may copy the identities to a data store associated with the target tenant, upload mapping data to the data store, and use that mapping data to map the identities copied to the data store to the corresponding plurality of mail users in the target tenant. For each of the identities mapped, the system may copy at least one or more attributes of the respective identity from the data store to the respective corresponding mail user in the target tenant.