Blocking Access To Inbox/Saved PMs

Is it possible to block a user from accessing their PMs?

We've had a difficult situation in our community with an individual. To spare you the details, tl;dr he received a PM a while ago containing someone's personal details, but due to said difficult situation that person is now concerned that their personal details will be misused. The best solution would be to just delete the message, but admins can't access people's PMs. Is it possible to stop someone accessing their PMs? I know there is an option to remove the ability to send them, but I don't know it that also prevents then from accessing their inbox.

Dear @Urvogel

what you can do is preventing the user from sending new private messages - but I am afraid that is the only option, you can't delete his/her private messages unfortunately.
edit: I checked, and if you disable that option the user can still access his former messages, he simply cannot send new ones

To disable PMs:

If the PM contain anything  relating to accounts, the sender will need to change passwords to the accounts.   If it was an address or phone number, the sender will need to careful about calls and mail.  If the member who caused issues try to contact the sender outside of the forum, the sender will need to contact the local authorities.

is this solved?