On Wed, Jul 24, 2019 at 09:29:47AM -0500, David Wright wrote:
However, I would not award +1 to the MUAs that, we are told, truncate the message, or even just the line, at the first NUL byte. That could yield a message with a very different sense from what the sender wrote.
And that is what happens when you do something that is out of spec for the protocol--the recipient's behavior is undefined and possibly suboptimal. (A NUL is specifically disallowed per RFC 2822.)