From Forum Nokia Wiki

Many devices that support sending e-mail (as Short Message Service(SMS), Multimedia Messaging Service(MMS), or another format) support the mailto: scheme, an extension that can initiate an e-mail message:

<a href="mailto:john.smith@domain.net">Message to John</a>

You can also specify a default subject and/or body as get parameters in the URL:

<a href="mailto:john.smith@domain.net?subject=
The%20Subject&amp;body=this%20is%20the%20message">Message to John</a>