[Mailman-Users] Mailman brokenly base64-encoding all messages

[Jon Ribbens]

I'm using Mailman 2.1.22 packaged by Ubuntu 16.10.

It appears that on one (but I think not all) of my mailing lists,
Mailman is base64-encoding every single message. Yes, including
ones that 100% definitely contain only ASCII characters. Does anyone
know why Mailman would be doing this?

You might say that base64-encoding all messages shouldn't be
a problem, and you'd be partly right. However there is also another
problem: Mailman is getting the line break encoding wrong in its
base64-encoded messages - by which I mean the encoded representation
of line breaks inside the base64 data. As per RFC 2045 s6.8: "line
breaks must be converted into CRLF sequences prior to base64 encoding"
but Mailman is outputting just LF.

The latter problem definitely appears to be a bug in Mailman,
or perhaps the Python 'email' package. The former seems likely to
be a configuration issue, but it's not obvious to me where.