RT message has lines too long for transport


I did a fresh installation of 5.0.4, and it seems that the default templates for mail are broken.
If someone how has not the permission to write to a queue did it, the response mail failed with
“message has lines too long for transport”.

The limit for lines changed with RFC5322:

What did the response email look like? Is there something in the email that confirms it came from RT? That doesn’t sound like a message RT would send, so I suspect it may have come from the MTA that received the message.