Microsoft Forefront Security for Exchange Server is the cause of this messsage:
The original contents of this file have been replaced with
this message because of its characteristics.
File name: ‘winmail.dat’
Virus name: ‘CorruptedCompressedFile’
Goto Forefront Server Security Administrator > Settings> General Options > Scanning
Goto checkbox name “Delete Corrupted Compressed File”
Uncheck the box and test