MailboxConfigItem.ReadWrite

const options = {
	authProvider,
};

const client = Client.init(options);

const userConfiguration = {
  id: 'MyApp',
  binaryData: 'SGVsbG8=',
  xmlData: 'V29ybGQ=',
  structuredData: [
    {
      keyEntry: {
        type: 'byte',
        values: [
          '100'
        ]
      },
      valueEntry: {
        type: 'boolean',
        values: [
          'true'
        ]
      }
    },
    {
      keyEntry: {
        type: 'integer32',
        values: [
          '-32'
        ]
      },
      valueEntry: {
        type: 'integer64',
        values: [
          '64'
        ]
      }
    },
    {
      keyEntry: {
        type: 'unsignedInteger32',
        values: [
          '32'
        ]
      },
      valueEntry: {
        type: 'unsignedInteger64',
        values: [
          '64'
        ]
      }
    },
    {
      keyEntry: {
        type: 'string',
        values: [
          'DateTime'
        ]
      },
      valueEntry: {
        type: 'dateTime',
        values: [
          '2025-10-23T01:23:45.0000000+00:00'
        ]
      }
    },
    {
      keyEntry: {
        type: 'byteArray',
        values: [
          'AQECAwUI'
        ]
      },
      valueEntry: {
        type: 'stringArray',
        values: [
          'Hello',
          'World'
        ]
      }
    }
  ]
};

await client.api('/me/mailFolders/inbox/userConfigurations')
	.version('beta')
	.post(userConfiguration);

Import-Module Microsoft.Graph.Beta.Mail
# A UPN can also be used as -UserId.
Get-MgBetaUserMailFolderUserConfiguration -UserId $userId -MailFolderId $mailFolderId -UserConfigurationId $userConfigurationId

# Code snippets are only available for the latest version. Current version is 1.x
from msgraph_beta import GraphServiceClient
# To initialize your graph_client, see https://learn.microsoft.com/en-us/graph/sdks/create-client?from=snippets&tabs=python

result = await graph_client.me.mail_folders.by_mail_folder_id('mailFolder-id').user_configurations.by_user_configuration_id('userConfiguration-id').get()