Policy
Prevent MAPI services from being added
By default, any MAPI service can be added to a user profile as an Outlook account. This setting allows you to prevent users from adding a specific MAPI services on the list of services. To prevent adding a MAPI service, append the name of the service to the list of services stored in this setting, separated by from a previous name by a semi-colon (;). For example, if you wanted to prevent adding the Outlook Mobile Service and Live Meeting Transport, you would configure this setting "MSOMS;LiveMeeting".
c36a9ae4e9c7 L_PreventMAPIservicesfrombeingadded Registry
Copy registry mappings
HKCU\software\policies\microsoft\office\16.0\outlook\options\disablecreateservicesPolicy notes
By default, any MAPI service can be added to a user profile as an Outlook account. This setting allows you to prevent users from adding a specific MAPI services on the list of services. To prevent adding a MAPI service, append the name of the service to the list of services stored in this setting, separated by from a previous name by a semi-colon (;). For example, if you wanted to prevent adding the Outlook Mobile Service and Live Meeting Transport, you would configure this setting "MSOMS;LiveMeeting".