Permissions for Recipient Verification

Hello,

can someone tell me which user rights are necessary for a successfully ad-directory recipient verification in SFOS 18.

we have set up our active directory server with a user who has read access from ldap.

unfortunately that doesn't seem to be enough. with an administrator who has full authorization, everything works fine. We would like to give the user only the absolutely necessary rights. Does somebody has any idea?

Thanks a lot

Manuel