Only allow users with fewer than X posts to private message moderators and administra

[Chunky Monkey]

Hello,

Does anyone know if there is a mod that allows you to specify that users with fewer than X posts can only send private messages to and receive private messages from members of specific usergroups, such as moderators and administrators? I am looking for something like this for 3.8.4. I have searched the forums extensively.

Alternatively, do you know what I might edit in private.php to achieve the same? I tried checking the values posted when I submit a new private message, but the only values in $_POST appear to be "Array ( [ajax] => 0 )" :-(

Thanks so much