You can block incoming email from a specific user coming into your organisation by modifying the Internet Mail Connector.
Run the Exchange Administrator program and drill down into the organisation as follows
Organisation | Site | Configuration | Connections | IMC
Go to the properties of the Internet Mail Connector
Connections tab | Message Filtering button
Enter the user’s SMTP address here and the internet mail service will reject mail from that user.
If you want the messages to be saved to the Turf directory, create a directory named “turfdir” at the root of C: (if you want to create it elsewhere, check Q193926.)
Do not forget to restart the Internet Mail Service following the modifications.