Comment 1 for bug 1670033

If you position the cursor to the end of the last line, you should be able to press enter/return and add a new line. You should be able to ensure in the web GUI that msg_footer ends with a new-line. If this doesn't work, it would seem to be a browser issue.

The base64 encoding is a Debian modification having to to with their changing Mailman's character set for English (and all other languages) to UTF-8.