Set OtherMails via Graph

Set-OtherMails.ps1

[CmdletBinding()]Param(
    [Parameter(Mandatory)]
    [String]
    $UserPrincipalName,

    [Parameter(Mandatory)]
    [AllowEmptyString()]
    [String]
    $NewValue,

    [Parameter()]
    $Tenant,

    [Parameter()]
    $Path = '{0}\credential.clixml' -f $PSScriptRoot
)

# Load in the client ID and secret from the encrypted config file.
try {
    $Credential = Import-Clixml -Path $Path -ErrorAction STOP
}
catch {
    Write-Error -ErrorAction STOP -Message ('Failed to load credential file: {0}' -f $PSItem.exception.message)
}

# Get a token that we can use to make the update.
try {
    $requestToken = @{
        Grant_Type      = 'client_credentials'
        Client_Id       = $Credential.UserName
        Client_Secret   = $Credential.GetNetworkCredential().Password
        Scope           = 'https://graph.microsoft.com/.default'
    }
    $requestSplat = @{
        Uri             = "https://login.microsoftonline.com/$Tenant/oauth2/v2.0/token"
        Method          = 'POST'
        Body            = $requestToken
        ErrorAction     = 'STOP'
    }
    $tokenResponse = Invoke-RestMethod @requestSplat
    $tokenHeader = @{Authorization="Bearer $($tokenResponse.access_token)"}
}
catch {
    Write-Error -ErrorAction STOP -Message ('Failed to request Graph token: {0}' -f $PSItem.exception.message)
}

# Check to make sure we can find the user first.
try {
    $apiUrl = 'https://graph.microsoft.com/v1.0/users/{0}' -f $UserPrincipalName
    $apiUrlAttributes = '{0}?$select=id,displayName,otherMails' -f $apiUrl
    $null = Invoke-RestMethod -Headers $tokenHeader -Uri $apiUrlAttributes
}
catch {
    Write-Error -ErrorAction STOP -Message ('Failed to query for {0}: {1}' -f $UserPrincipalName,$PSItem.exception.message)
}

# Update the current value of otherMails
try {
    if ($null -like $NewValue) {
        $attributeJSON = @{
            "otherMails" = @()
        } | ConvertTo-Json
    }
    else {
        $attributeJSON = @{
            "otherMails" = @("$NewValue")
        } | ConvertTo-Json
    }

    $updateSplat = @{
        Headers         = $tokenHeader
        Uri             = $apiUrl
        Method          = 'Patch'
        ContentType     = 'application/json'
        Body            = $attributeJSON
        ErrorAction     = 'STOP'
    }
    Invoke-RestMethod @updateSplat
}
catch {
    Write-Error -ErrorAction STOP -Message ('Failed to update {0} on {1}: {2}' -f $Attribute,$UserPrincipalName,$PSItem.exception.message)
}