la prima riga del codice form era sbagliata, questa è corretta credo :

<form ACTION="<%=MM_editAction%>" method="POST" name="form1" id="form1" onsubmit="MM_goToURL('parent','regmail.php');return document.MM_returnValue">

Questo è il codice del form:

<form ACTION="<%=MM_editAction%>" method="POST" name="form1" id="form1">
<p> </p>
<table width="312" align="center">
<tr valign="baseline">
<td width="89" align="right" nowrap="nowrap">Nome:</td>
<td width="211"><input name="nome" type="text" id="nome" size="30" /></td>
</tr>
<tr valign="baseline">
<td nowrap="nowrap" align="right">Cognome:</td>
<td><input name="cognome" type="text" id="cognome" value="" size="30" /></td>
</tr>
<tr valign="baseline">
<td nowrap="nowrap" align="right">e-mail:</td>
<td><input name="e-mail" type="text" id="e-mail" value="" size="30" /></td>
</tr>
<tr valign="baseline">
<td nowrap="nowrap" align="right">Username:</td>
<td><input name="username" type="text" id="username" value="" size="30" /></td>
</tr>
<tr valign="baseline">
<td nowrap="nowrap" align="right">Password:</td>
<td><input name="password" type="password" id="password" value="" size="18" />
<input name="REGISTRA" type="submit" id="REGISTRA" value="Registra" />
 </td>
</tr>
<tr valign="baseline">
<td nowrap="nowrap" align="right"> </td>
<td> </td>
</tr>
</table>
<p>
<input type="hidden" name="MM_insert" value="form1" />
</p>
</form>

Il problema è che non so come integrare il file per l'invio e-mail!!

Ciao anche a te Marco