UpdateWorkDays.psm1 is a PowerShell script to update Exchange Server mailbox calendar's "WorkDays" property.
It defines functions Update-WorkDays and Get-Token.

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Background

When you use Exchange Server's cmdlet to configure WorkDays to either "Weekdays" or "AllDays", Outlook does not understand these literal values.

e.g.

Set-MailboxCalendarConfiguration user01 -WorkDays AllDays  

As a result, the calendar looks "grayed-out".
This script fixes this situation by modifying the WorkDays value as follows:

• if "AllDays" --> "Sunday Monday Tuesday Wednesday Thursday Friday Saturday"
• if "Weekdays" --> "Monday Tuesday Wednesday Thursday Friday"

Requirement

• PowerShell v3 or later
• .NET Framework 4.6.1 or later

The following modules need to be placed under "modules" sub folder where the script file is. These are included in the release package.

• Microsoft Exchange Web Services Managed API 2.2
• MSAL.NET
• MSAL.NET Extensions

How to use

1. With Exchange Management Shell, grant ApplicationImpersonation role to a user who runs the script

   This script uses EWS Impersonation to access the target mailbox.

   e.g.

   New-ManagementRoleAssignment -Role 'ApplicationImpersonation' -User contoso\administrator  

2. Start PowerShell and Import-Module the script

   e.g.

   Import-Module 'C:\tmp\UpdateWorkDays.psm1'  

3. If you are using Modern Auth, get a token

   You can use Get-Token included in this script.

   e.g.

   $token = Get-Token -ClientId '63ce5cc6-c944-4baa-83d1-5cac8cdf487e' -Scopes 'https://outlook.office365.com/EWS.AccessAsUser.All'  

   * Client ID above is just an example. Use your own application's Client ID.

4. Execute Update-WorkDays

   mandatory parameters:

   name	meaning
   Server	Name of the Exchange server. For Exchange Online, outlook.office365.com
   TargetMailboxSmtpAddress	Target mailbox whose WorkDays you are trying to fix

   Conditionally mandatory parameters:

   * These parameters are mutually exclusive: Credential for legacy auth and Token for Modern auth.

   name	meaning
   Credential	Credential used for Legacy auth
   Token	Access token used for Modern auth

   Optional parameters:

   name	meaning
   EwsManagedApiPath	Path to Microsoft.Exchange.WebServices.dll
   EnableTrace	Switch parameter to enable tracing
   TraceFile	Path to a trace file

   e.g.

   Update-WorkDays -Server 'myExchange.contoso.local' -TargetMailboxSmtpAddress 'user01@contoso.local' -Credential (Get-Credential) -EnableTrace -TraceFile 'C:\temp\trace.txt'  

   e.g.
   * The following Client ID is just an example. Use your own application's Client ID.
   * If your application is registered as a muti-tenant app, then you do not need to provide TenantId parameter for Get-Token (Just as this example). If your application is a single-tenant app, then specify the tenant name or GUID in TenantId.

   $token = Get-Token -ClientId '63ce5cc6-c944-4baa-83d1-5cac8cdf487e' -Scopes 'https://outlook.office365.com/EWS.AccessAsUser.All'  
   Update-WorkDays -Server 'outlook.office365.com' -TargetMailboxSmtpAddress 'user01@contoso.com' -Token $token.AccessToken -EnableTrace -TraceFile 'C:\temp\trace.txt'  

About Modern Auth

If you are using Modern Auth, then you first need to register an application in your Azure AD.

• Get-Token uses https://login.microsoftonline.com/common/oauth2/nativeclient as the default Redirect URI. If your application uses a different URI, provide it to RedirectUri.
• For API Permissions, add Exchange's EWS.AccessAsUser.All

Reference

• Authenticate an EWS application by using OAuth

License

Copyright (c) 2020 Ryusuke Fujita

This software is released under the MIT License.
http://opensource.org/licenses/mit-license.php

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.