Create Exchange Mailboxes via PowerShell

#####################################################################
#Title: Exchange Mailbox Creation
#Authors: Michael Ansaldi
#Date: 08/15/2012
#
#1)Make sure you have Quest Active Roles Snap-in installed
#2)Make sure you have Exchange Management Shell installed
#3)Load Quest ActiveRoles Snap-in
#PS C:> Add-PSSnapin Quest.ActiveRoles.ADManagement
#4)CSV file should have first line as headers "username","domain"
#
#Creates Exchange mailboxes based off of a CSV providing username and domain values. Supports different domains if trust is established ahead of time... Outputs to a path defined by user.
#####################################################################

###############
#Set variables#
###############
$storageGroup = "ExchangeServerName\Storage Group Name\StorageGroupFileName"
$logFile = "PathToOutputLogTo\MailboxCreation_{0:yyyyMMdd_HHmm}.log" -f (Get-Date)
$CSVPath = "PathToCSVFile\exchangeusers.csv"

##################
#Custom Functions#
##################
Function LogWrite ([string]$logString)
{
   Add-content $logFile -value $logString
}

Function ValidationCheck ($importedUsers)
{

    #Create an array for users to be processed
    [array]$ltp = $null;

    #Log formatting :-)
    LogWrite "*Validation Check*"
    LogWrite "----------------"


    ForEach($importedUser in $importedUsers){

        Try {

            switch($importedUser.domain) {
                "domain1" {
                    $adAcct = Get-ADUser -Identity $importedUser.username -Server domain1.com
                }

                "domain2" {
                    $adAcct = Get-ADUser -Identity $importedUser.username -Server domain2.com
                }

                default {LogWrite "$($importedUser.username) did not have a valid domain name, check the CSV"}
            }

            If ($adAcct -ne $null) {
                #Check Exchange for existing mailbox
                If($uMailbox = Get-Mailbox -Identity $importedUser.username) {
                        #Found existing mailbox, log it, don't add to list
                        LogWrite "$($importedUser.username) already has a mailbox... skip."
                }
                Else {
                        #Mailbox doesn't exist, add user to the list of boxes to process
                        $ltp += $importedUser
                        LogWrite "$($importedUser.username) will be processed."
                }
            }
        }
        Catch {

            LogWrite "$_ check AD and confirm a user account exists"
        }


    }

    #Log formatting :-)
    LogWrite ""

    return $ltp
}

######################
#Import New Users CSV#
######################

Try
{
    #Log formatting :-)
    LogWrite "*Mailbox Creation Script*"
    LogWrite "----------------"
    LogWrite "*CSV Import Process*"
    LogWrite "----------------"

    #Import CSV
    $importedUsers = Import-Csv $CSVPath

    #Clean up blank username records
    $importedUsers = @($importedUsers | Where-Object {$_.username -ne ""})

    LogWrite "Users imported: $($importedUsers.Count)"
    LogWrite "Import complete!"
    LogWrite "----------------"
}
Catch
{
    #Write to log file
    LogWrite "Failed to import CSV..." [System.Exception]
}

###########################
#Scan imported data errors#
###########################

#Store results of the validation in an array, defined as an array because if not and only one result is returned, PoSH decides to treat it as a string
[array]$fList = $null
$fList = ValidationCheck $importedUsers

#Display final list count
if ($fList.Count -gt 0){
    LogWrite "Users to process: $($fList.Count)"
}
else{
    LogWrite "Users to process: 0"
}
LogWrite "----------------"


##################
#Create Mailboxes#
##################

#Log formatting
LogWrite "Mailbox Creation"
LogWrite "----------------"


if ($fList.Count -gt 0){

    ForEach($item in $fList){

            Try
            {

                #Build UPN (accepted by Enable-Mailbox for identity parameter, allows us to account for different domains
                Switch ($item.domain)
                {
                    "domain1" {$upn = $item.username + '@domain1.com'}
                    "domain2" {$upn = $item.username + '@domain2.com'}
                    default {$upn = "Issue with switch case"}
                }

                #Enable mailbox
                if(Enable-Mailbox -Identity $upn  -Database $storageGroup)
                {
                    LogWrite "$($item.username) mailbox created succesfully!"
                }

            }
            Catch
            {
                LogWrite "$($item.username) had an error when creating the mailbox."
            }
        }
}
else{
    LogWrite "No mailboxes to create!"
}