Lately, a lot of people have been posting messages here that are malformatted, with long lines stretching out indefinitely. You can see this when you look at the web archive, where you sometimes have to scroll a mile to the right to see all of the message. This is contrary to the standards of RFC 2822, which recommend that there be a hard break after lines of no more than 79 characters.
More info: http://mailformat.dan.info/body/linelength.html
Info on configuring various mail programs to follow standards: http://mailformat.dan.info/config/
List archives online, where you can see the problem: http://lists.wikimedia.org/pipermail/wikien-l/