On the Barracuda Email Security Gateway 300 and higher, email recipients can be validated with your existing LDAP server. Configuration of LDAP lookup is done at the domain level. From the DOMAINS > Domain Manager page, after clicking Manage Domain for the selected domain, you’ll configure LDAP on the USERS > LDAP Configuration page. click the Help button on that page for details about entering your server details. If LDAP is not configured, the Barracuda Email Security Gateway will do SMTP recipient verification through RCPT TO commands.
LDAP server types supported include Active Directory, Novell eDirectory, Domino Directory and OpenLDAP.
Explicit Users to Accept For (Valid Recipients)
If LDAP lookup is not being used for recipient verification, the Barracuda Email Security Gateway provides a local database with which email recipients can be compared for validation. Valid Recipients (Explicitly Accepted Users) can be specified either at the global level from the ADVANCED > Explicit Users page or at the per-domain level from the DOMAINS > Domain Manager > USERS > Valid Recipients page. Note that the number of entries in the text box for Explicitly Accepted Users and Alias Linking is limited by model: on the Barracuda Email Security Gateway 600 and lower, the maximum is 1000 per domain, and on the Barracuda Email Security Gateway 800 and above, the limit is 5000 per domain.
To administer the local database, either at the global or domain level, fill in the text box in the Explicit Users to Accept For section of the page, entering each email address for which the Barracuda Email Security Gateway should accept email. If you select Yes for the Only accept email for these recipients feature, email will REJECTED for any email recipients not in the list. Note that domain-specific lists override the global list.
Alias linking allows quarantined email from multiple accounts to be directed to one account when using per-user quarantine. In the ADVANCED > Explicit Users page you can specify the email addresses to be linked together in the Explicit Users to Accept For and Alias Linking text box. click the Help button on that page for more details.The quarantine account for all of the linked email addresses will be associated with the first email address. Make sure to also enter the first email address on a separate line as well. In this way, a "catchall" account can be created to receive all quarantined emails from a particular domain.