Many LDAP clients expect to see the mail attribute in Account and other Domain Object records. But, by default, CommuniGate Pro does not store such an attribute in those directory records.
If the LDAP module has to return such a record (a record of the CommuniGateAccount, CommuniGateMailList, or CommuniGateGroup object class), and that record does not contain the mail attribute, the LDAP module can compose that attribute on-the-fly, using the Object record DN: it takes the uid value from the DN (Account/Object name), the cn attribute value (Domain name), and merges them using the @ symbol to build the uidValue@cnValue mail attribute value. As a result, when an object is renamed (its record uid attribute is changed), or when the Domain is renamed (the cn attribute in the object DN is changed), the mail attribute is automatically updated.
Since the mail attribute is not stored in the Directory records by default, all search filters that use the mail attribute can be modified internally to use the uid attribute instead. If the search operation is "equals to", and the search string contains the @ symbol, only the part of the string before that symbol is used.
These two features can be enabled or disabled using the Domain Integration page in the Users realm of the WebAdmin Interface:
Ignore objectCategory filters: Some clients (including Microsoft Outlook) always send their LDAP search requests using filters checking for certain objectCategory attribute values. Since this attribute is not included into CommuniGate Pro Account records by default, you would have to create this attribute as a Custom one, and put a "proper" value into each Account settings.
This option tells the LDAP server to ignore all "objectCategory equals value" search operations (the Server treats these operations as the constant true-values).