Mail enabled lists - using powershell to disable or enable?

I'm moving hundreds of mail enabled lists from one sharepoint farm to another. Once they're moved I need to disable the lists for email on the old farm and enable them on the new farm. I'd like to find a way to script this with powershell. So far I've tried:

$spWeb = get-spweb http://intranet/site
$spList = $spWeb.GetList("/site/Lists/List")
$spList.CanReceiveEmail = "False"
$spList.Update()

However, when trying to set the value to False, I get an error "CanReceiveEmail is a ReadOnly property."

Has anyone found a way to do this?