Exchange 2007 Management console doesn’t allow to use a mail-enabled public folder as a destination for transport rules, so the only way it’s make the rule from PowerShell.
In the following example we’ll create a Transport rule that sends a blind copy to a mail-enabled public folder for each message sent by a user.
$Mailbox = "email@example.com"
$PublicFolder = "PF1mailenabled-pf-01"
$condition = Get-TransportRulePredicate From
$condition.Addresses = @(( Get-Mailbox $Mailbox ))
$action = Get-TransportRuleAction BlindCopyTo
$action.Addresses = @(( Get-MailPublicFolder $PublicFolder ))
New-TransportRule -name "From $Mailbox Send A Bcc To $PublicFolder" -Conditions @($condition) -Actions @($action)