Create-ResMailboxes.ps1

[CmdletBinding()]
param(
    [ValidateScript({Test-Path $_ -PathType Leaf})]
    [Parameter(Mandatory=$True,Position=1)][string]$CSV
)

Import-Module ActiveDirectory
if(!(Get-PSSnapin |
    Where-Object {$_.name -eq "Microsoft.Exchange.Management.PowerShell.E2010"})) {
      ADD-PSSnapin Microsoft.Exchange.Management.PowerShell.E2010
}

$start = Get-Date
$domain = Get-ADDomain
$addomain = $domain.Forest
$domaindn = $domain.DistinguishedName
$logfile = ".\CreateResMailboxes.log"
$nl = "`r`n"
$ou = "OU=General Mailboxes,OU=Exchange,$domaindn"

function writelog([string]$message) {
    $timestamp = Get-Date
    $fc = "White"
    if($message.contains("ERROR")) {$fc ="Red"}
    Add-content $logfile -value "$timestamp : $message"
    Write-Host $message -ForegroundColor $fc
}

writelog "Importing resource mailboxes from $csv at $start"
Write-Host $nl

Import-Csv $csv | ForEach-Object {
    Set-Variable -Name testmb -Value $null -Scope 0
    $upn = $_.SamAccountName + "@" + $addomain
    $name = $_.DisplayName
    $alias = $_.Alias
    $email = $_.PrimarySmtpAddress
    $testmb = Get-Mailbox $alias -ErrorAction SilentlyContinue
    if($testmb -eq $null) {
        writelog "Creating mailbox $name ($email)"
        New-Mailbox -name $name -DisplayName $name -Shared -Alias $alias -UserPrincipalName $upn -PrimarySmtpAddress $email -OrganizationalUnit $ou
    }
    else {
        writelog "Mailbox  $name ($email) already exists, skipping."
    }
}

$end = Get-Date
$elapsed = $end - $start
Write-Host $nl
writelog "Finished import at $end ($elapsed)"