$resfile = New-Item -ItemType file -Path liste_external_contacts.csv -Force
 
Add-Content -Path $resfile -Value "MailContactDisplayName,MailcontactAlias,MailcontactOrganizationalUnit,MailcontactExternalEmailAddress"
 
Get-MailContact -ResultSize unlimited | ForEach-Object {
 
	Add-Content -Path $resfile -Value "$($_.DisplayName),$($_.alias),$($_.OrganizationalUnit),$($_.ExternalEmailAddress)"
 
}