The user mail and calendar service is defined in a Class-of-Service definition called standardUserMailCalendar:
# # Definition for user mail and user calendar service bundle # dn: cn=standardUserMailCalendar,<ugldapbasedn> changetype: add objectclass: top objectclass: LDAPsubentry objectclass: extensibleObject objectclass: cosSuperDefinition objectclass: cosClassicDefinition cosTemplateDn: o=mailcalendaruser,o=cosTemplates,<ugldapbasedn> cosSpecifier: inetCos cosAttribute: icsPreferredHost cosAttribute: icsDWPHost cosAttribute: icsFirstDay cosAttribute: icsQuota cosAttribute: mailAllowedServiceAccess cosAttribute: mailMsgMaxBlocks cosAttribute: mailquota cosAttribute: mailmsgquota daServiceType: calendar user daServiceType: mail user NOTE: When the Delegated Administrator configuration program installs the standardUserMailCalendar 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 users.