In a Microsoft Exchange Server 2016 environment, the Transport service may not send email messages that contain an attachment that was encoded with Unix-to-Unix Encoding (UUE) type. When this issue occurs, you experience the following exception:
Failed to process message due to a permanent exception with message. The message content has become corrupted.
This issue occurs because the UUE attachment size exceeds the defined MaximumBytes of the Transport's UUDecoder.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.