There are two types of Authentications that you can choose while creating a trust
1. Domain Wide Authentication
2. Selective Authentication
Domain Wide Authentication: When a trust is created using domain wide authentication then by default users of the trusted domain have access to all the available shared resources of the trusting domain.
Selective Authentication: When a trust is created using selective authentication then by default users of the trusted domain do NOT have any access to the resources of the trusting domain (Not even on the machines of the trusting domain)
In this scenario, administrator has to manually add the user whom we want to grant access on the resource in the trusting domain. In case of a machine account of a trusting domain, users has to be explicitly added in the ACL of the machine account and has to be given "Allowed to Authenticate" permission. Only after doing this, a user will be able to use the machine of the trusting domain to login
