Create a mailbox subfolder with MS Graph

Question

I am using PowerShell to connect to M365 mailboxes and am able to create a folder as per: https://learn.microsoft.com/en-us/graph/api/user-post-mailfolders however, I also need to create subfolders, and am unable to find any syntax help to do so.

Here is the script I'm using to create the folder: The variable $Folders only creates root level folders, no subfolders.

$Mailboxes = @("******@myemail.com")  
$Folders = @("FolderRoot","SubFolder")  
  
$AppId = "*******"  
$AppSecret = "********"  
$Scope = "https://graph.microsoft.com/.default"  
$TenantName = "**********"  
  
$Url = "https://login.microsoftonline.com/$TenantName/oauth2/v2.0/token"  
  
Add-Type -AssemblyName System.Web  
  
$Body = @{  
    client_id = $AppId  
	client_secret = $AppSecret  
	scope = $Scope  
	grant_type = 'client_credentials'  
}  
  
$PostSplat = @{  
    ContentType = 'application/x-www-form-urlencoded'  
    Method = 'POST'  
    # Create string by joining bodylist with '&'  
    Body = $Body  
    Uri = $Url  
}  
  
$Request = Invoke-RestMethod @PostSplat  
  
$Header = @{  
    Authorization = "$($Request.token_type) $($Request.access_token)"  
}  
  
foreach($mailbox in $Mailboxes) {  
  
    $Uri = "https://graph.microsoft.com/v1.0/users/$mailbox/mailFolders"  
  
    $Mailboxfolders = Invoke-RestMethod -Uri $Uri -Headers $Header -Method Get -ContentType "application/json"  
    $MailboxfoldersList = $Mailboxfolders.Value.Displayname  
    $NextPage = $Mailboxfolders.'@Odata.NextLink'  
     
    While($NextPage -ne $Null) {  
        $Mailboxfolders = Invoke-RestMethod -Uri $NextPage -Headers $Header -Method Get -ContentType "application/json"  
        $MailboxfoldersList += $Mailboxfolders.Value.Displayname  
        $NextPage = $Mailboxfolders.'@Odata.NextLink'  
    }  
  
    foreach($Folder in $Folders) {  
  
$Body = @"  
{  
"displayName": "$Folder"  
}  
"@  
  
        ## Output current operation  
  
        Write-Host "Mailbox: $mailbox`nMailboxfolders: $($MailboxfoldersList)`nFolder wanted: $folder"  
  
        if($($MailboxfoldersList) -contains $folder) {  
            write-host "$folder folder already found at mailbox $mailbox.`n"  
        }  
  
        else {  
            $Newfolder = Invoke-RestMethod -Uri $Uri -Headers $Header -Method Post -Body $Body -ContentType "application/json"  
            write-host "Created new folder: $($Newfolder.displayName) to mailbox $mailbox!`n"  
        }  
    }  
}  
  

Answer 1

The MailFolders Endpoint

"https://graph.microsoft.com/v1.0/users/$mailbox/mailFolders"

Lets you list and create a folder in the MailboxFolderRoot so it equivalent to

/MailFolders('MsgFolderRoot')/childfolders

There is no way of doing a deep traversal with the Graph at the moment (meaning you traverse every layer of childfolders) you can do one layer using expand eg

https://graph.microsoft.com/v1.0/me/mailfolders?expand=childFolders

This would for instance give you subfolders of the Inbox Folder in the ChildFolders property eg

            "id": "AQMk",
            "displayName": "Inbox",
            "childFolders@odata.context": "https://graph.microsoft.com/v1.0/$metadata#users('150bb06c-1c9a-4ac2-8b55-8cf15854b555')/mailFolders('AQ-0Y6jBNnUCxQousINAAAAIBDAAAAA%3D%3D')/childFolders",
            "childFolders": [
                {
                    "id": "AAA=",
                    "displayName": "aa",
                    "parentFolderId": "AQM==",
                    "childFolderCount": 0,
                    "unreadItemCount": 178,
                    "totalItemCount": 209,
                    "isHidden": false
                },

There are a few different ways of solving your problem if all you wanted to do was create subfolders of the Inbox folder (or other wellknown folder) then if you changed line 36 to

$Uri = "https://graph.microsoft.com/v1.0/users/$mailbox/mailFolders/Inbox/ChildFolders"

all the logic in your script should work okay else you should find the FolderId of the parentFolder you want to create those folders under

Answer 2

Thank you for answering. I kept failing at the /childFolders part, as I realized (after reading the error messages) that it was asking for the [id] of the parent folder, so I got it to work by doing the following (I'm sure there's a more elegant way):

        if($($MailboxfoldersList) -contains $folder) {
            write-host "$folder folder already found at mailbox $mailbox, creating subfolder.`n"
        }

        else {
            $Newfolder = Invoke-RestMethod -Uri $Uri -Headers $Header -Method Post -Body $Body -ContentType "application/json"
            write-host "Created new folder: $($Newfolder.displayName) to mailbox $mailbox!`n"
            $ParentFolder = $Newfolder.id
            $UriSub = "https://graph.microsoft.com/v1.0/users/$mailbox/mailFolders/$ParentFolder/childFolders"
        }
    }
    foreach($subFolder in $subFolders) {

        $Body2 = @"
        {
            "displayName": "$subFolder"
        }
"@

        if($($MailboxfoldersList) -contains $subfolder) {
            write-host "$subfolder folder already found at mailbox $mailbox.`n"
        }

        else {
            $NewSubfolder = Invoke-RestMethod -Uri $UriSub -Headers $Header -Method Post -Body $Body2 -ContentType "application/json"
            write-host "Created new subfolder: $($NewSubfolder.displayName) in $Folder to mailbox $mailbox!`n"
        }
    }