Regex in mimemail_headers strips allowed characters

The plus symbol ("+") is an allowed character in email usernames. There may be others not in the regex. Oh, yeah, underscores. I think the preg_match line should at least be:

preg_match('/[a-z0-9\-\.\+_]+@{1}[a-z0-9\-\.]+/i', $from, $matches);

One could make the argument for a more inclusive expressions like:

preg_match('/[^\s<]+@{1}[^\s\.]+\.[^\s>]+/i', $from, $matches);

But I'm not an expert and it may include more than it really should.