MIT Mailman User Guide:
offers the option to set the default language for a list, as well as options
for other languages supported by the list administrative interface.
the options available on the Language Options Screen:
Note however, that if your mailing list receives both encoded and unencoded
subject headers, you might want to choose As needed. Using this setting, Mailman
will not encode ASCII prefixes when the rest of the header contains only ASCII
characters, but if the original header contains non-ASCII characters, it will
encode the prefix. This avoids an ambiguity in the standards which could cause
some mail readers to display extra, or missing spaces between the prefix and
the original header.