The only thing I know that can help is <a href="mailto:...">.
However, I need to warn you of a Google toolbar/mail bug that may affect other email clients. They've apparently pruned it from the toolbar's forum since I reported it, but it crams the message all on one line. URLs have a mechanism to allow special characters such as newlines to be sent, but Google doesn't fully implement it. To test your own client, save this link in an HTML file and click it:
Code:
<a href="mailto:user@example.com?body=foo%0d%0abar">Do as ooga booga do.</a>
In Gmail, I see "foo bar" with no newline (which I encoded properly in the URL).
Anyway, if you want to use this (preferably from PHP), see here for all the available options.
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