Powershell sharepoint set user email

gistfile1.sh

[system.reflection.assembly]::LoadWithPartialName("Microsoft.Sharepoint")

$siteUrl = "http://sharepoint/"
$site = New-Object Microsoft.SharePoint.SPSite($siteUrl)
$web = $site.rootweb

$email = 'mdnmdn@mymail.com'
$username = 'mdn'

$u = $web.EnsureUser($username)
$u.email = $email
$u.update()