Auto-Prune Private Message(s) with options

[Chrissicom]

Since I want to add a subscription feature to my board that should allow users to store unlimited private messages for an unlimited time I want to change the PM behaviour for normal registered users.

I want these things (always except admins and mods):
- I want to remove existing private messages that are older than xx days
- I want to remove existing private messages from inboxes until there are no more than 25 messages (oldest should be removed first of course)
- Private messages of registered users should be removed automatically when they become xx days old
- When someones inbox is full a notice should be bounced back to the sender

Maybe there is a mod for this already but then I couldn't find it. I need to implement this for vB 3.5.4

Thanks for your help!!