The user mail and calendar service is defined in a Class-of-Service definition called standardGroupMailCalendar:
# # Definition for group mail and group calendar service bundle # dn: cn=standardGroupMailCalendar,<ugldapbasedn> changetype: add objectclass: top objectclass: LDAPsubentry objectclass: extensibleObject objectclass: cosSuperDefinition objectclass: cosClassicDefinition cosTemplateDn: o=mailcalendargroup,o=cosTemplates,<ugldapbasedn> cosSpecifier: inetCos cosAttribute: mgrpMsgMaxSize cosAttribute: mailMsgMaxBlocks daServiceType: calendar group daServiceType: mail group NOTE: When the Delegated Administrator configuration program installs the standardGroupMailCalendar definition in the directory, the variable <ugldapbasedn>, shown above, is replaced by your root suffix (such as o=usergroup).
The two daServiceType attribute entries define this as a calendar service and mail service for groups.