[Mailman-Users] body text size limit

RFC 2822 section 2.1.1 and 2.2.3

2.1.1. Line Length Limits

There are two limits that this standard places on the number of
characters in a line. Each line of characters MUST be no more than
998 characters, and SHOULD be no more than 78 characters, excluding
the CRLF.
[...]

2.2.3. Long Header Fields

Each header field is logically a single line of characters comprising
the field name, the colon, and the field body. For convenience
however, and to deal with the 998/78 character limitations per line,
the field body portion of a header field can be split into a multiple
line representation; this is called "folding". The general rule is

that wherever this standard allows for folding white space (not
simply WSP characters), a CRLF may be inserted before any WSP. For
example, the header field:

Subject: This is a test

can be represented as:

Subject: This
is a test
[...]

The short answer: it's not Mailman, it's the python email library
that does it.

For more discussion, there was just a thread on this topic two weeks
ago. It starts here:
http://www.mail-archive.com/mailman-users%40python.org/msg49882.html

Terri