gistfile1.txt

$params = @{
    SearchBase = (Get-ADDomain).DistinguishedName
    Filter     = { proxyAddresses -like '*' }
    Properties = 'Displayname',
                 'SamAccountName',
                 'UserPrincipalName',
                 'ProxyAddresses',
                 'DistinguishedName'
}

Get-ADUser @params |
    Select-Object DisplayName, SamAccountName, UserPrincipalName,
        @{n="OU"; e={ $_.DistinguishedName -replace 'CN=[^=]+,' }},
        @{n="PrimarySMTP"; e={
            $upn = $_.UserPrincipalName
            ($_.proxyAddresses | Where-Object { $_ -clike 'SMTP:*' -and $_ -ne $upn }) -join ', ' }} |
    Export-Csv .\primarySMTPnotMatchUPN.csv -NoTypeInformation