set-mailbox script, Reply To email address

Hey Team, 

I have a request to accomplish the following.

1. Create several hundred user accounts , license them. 
2. set the smtp address on each of the users mailboxes
3. list of names coming from a spreadsheet 

I have successfully taken care of the 1st step using this command: 

$Importlist = Import-CSV Testlist.csv

foreach ($SingleImport in $importlist)

    {

    New-MsolUser -DisplayName $SingleImport.Name -Department "Agency OWNER - TSR" -UserPrincipalName $SingleImport.UPN -UsageLocation US -LicenseAssignment TenantNameUAT:STANDARDPACK -ForceChangePassword $False

    }

The first part works as stated. 

This part however does not work:

Set-Mailbox -identity $SingleImport.UPN -EmailAddresses "SMTP:$SingleImport.Email_id", "smtp:$SingleImport.UPN"

All i want to do with the above command is to: 1) Add a new SMTP Address, and set the new address as reply-to. 

Error Text: Cannot process argument transformation on parameter 'EmailAddresses'. Cannot convert value "System.Collections.ArrayList" to type "Microsoft.Exchange.Data.ProxyAddressCollection".

If i try using the @Add{SMTP:address} it fails with the error stating that another address is already set as reply. 

I just cant seem to get past the Array Error. 

Thanks, 

Robert