Add-PSSnapin Microsoft.SharePoint.PowerShell
$webApp = Get-SPWebApplication http://sharepoint/
foreach ($site in $webApp.Sites)
{
Write-Host "Opening" $site.Url
foreach ($web in $site.AllWebs)
{
Write-Host "Opening" $web.Url
if ($web.RequestAccessEmail -ne "")
{
$web.AddProperty("RequestAccessEnabledBackup", $web.RequestAccessEmail)
$web.RequestAccessEmail = ""
$web.Update()
Write-Host $web.GetProperty("RequestAccessEnabledBackup") "saved"
}
$web.Dispose()
}
$site.Dispose()
}