The LDAP connection is required for the recipient check (Spamfinder) and the automatic synchronisation of users (Spamfinder profiles, MailSealer licences, MailDepot access authorisations).
At the moment a direct access to Azure AD via REDDOXX is not possible, but you may have an Active Directory Server anyway.
In a standard installation of the Active Directory service on a Microsoft server, the LDAP parameter "ProxyAddresses" (which we need for the administration of the mail addresses) is not available.
This LDAP attribute is part of an Exchange installation and is provided via an Active Directory schema update (depending on the version of the Microsoft server).
Microsoft already provides detailed documentation on this (here for Windows 2003 Server):
https://docs.microsoft.com/de-de/security-updates/windowsrightsmanagementservices/18118867
If the ProxyAddresses attribute is available, it can be edited with the attribute editor in the Active Directory and filled with e-mail addresses.
Alternatively, Powershell scripts can be used for this.
In the appliance, you configure LDAP in the local domains.
With the LDAP query diagnosis, you can also check whether an LDAP query delivers valid results.