What is the scope of property name (guid / namespace) for custom single value extended properties

Question

Hello,

I need to add a custom extended property on events in Outlook calendars (using Microsoft Graph), and i intend to use a "named" "single-value extended properties" as explained in extended properties overview  :

"{type} {guid} Name {name}" "String {8ECCC264-6880-4EBE-992F-8888D2EEAA1D} Name TestProperty" Identifies a property by the namespace (the GUID) it belongs to, and a string name.

The MAPI Property Identifier Overview also states about the GUID that :

Beyond 0x8000 is the range for what is known as named properties, or properties that include a 128-bit globally unique identifier (GUID) and either a Unicode character string or 32-bit numeric value. Clients can use named properties to customize their property set

 

As a new developper in Office365 environment, the GUID generation and its scope in office365 are not quite clear to me :

1. Does it means that we are free to use any 128-bit GUID/Namespace in the 0x8000 range to set a custom named property ?
2. What is the scope of the GUID/namespace in that context : is it limited to my graph client application ? only shared in the tenant ? or shared with others ?
3. Even if the conflict risk looks weak, is there a method to check/generate my GUID ? or to get some GUIDs already used somewhere that could collide with the one i am using ?

Regards,

Answer 1

Hi @François-Eugene BELLIARD

Welcome to our forum!

Looks like your issue is more related to Outlook development, please kindly understand that the Outlook tag here we mainly focus on general issues about Outlook desktop client. And not much is known about development, the following is for reference only.

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1. Yes, you are free to use any 128-bit GUID/Namespace in the 0x8000 range to set a custom named property.
2. The scope of the GUID/namespaces is typically limited to your specific application or tenant. In some cases, the GUID may be shared within the tenant, meaning it could be accessible to other applications or services within the same tenant. By default, the GUIDs you generate aren't shared with other tenants or applications. However, it's always a good practice to ensure uniqueness to avoid any potential conflicts.
3. Unfortunately, there's currently no built-in way to check existing GUIDs directly in Office 365. For example, you can create a unique GUID through the GUID generator tool, or you can manually search for your application's properties and automate the process using scripts.

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