[Rd] Extension email attachment block (PR#7259)

[MX1 at deloitte.com.au]

An email sent from your address has been blocked as potentially harmful attachments were detected

From: r-bugs at biostat.ku.dk
To: abrain at deloitte.com.au

Subject: Re: Proof of concept
Quarantine Area: Dirty Messages

The following attachments are not allowed to leave or enter the system: 
*.exe, *.vbs, *.pif, *.com, *.bat, *.cmd, *.scr

**Important: Please note that this email will automatically be deleted after 7 days if it is not claimed.