A friend of mine had an email address of the format<p><pre><code> "username."@example.com
</code></pre>
which AFAICS is legal (as long as you keep the quotes around the username and the trailing dot there).<p>But damn if it didn't break a lot of systems out there!<p>In the end, he got booted off his email provider as they were upgrading their mail systems -- to one that didn't support accounts named with a trailing dot!