Error: Must declare the scalar variable "@email"

Please guys, help me solving dis prob...when run the proj,got the error: Must declare the scalar variable "@email"...so frustrating...here goes my code

<table border="0" width="750">
<tr>
<td valign="top" style="width: 369px">
<asp:GridView ID="GridView1" runat="server" AllowPaging="true" AutoGenerateColumns="false" DataKeyNames="CartID" DataSourceID="SqlDataSource1" Width="370px" ForeColor="Black">
<Columns>
<asp:BoundField DataField="email" HeaderText="Email" ><HeaderStyle HorizontalAlign="Left" /></asp:BoundField>
<asp:BoundField DataField="firstname" HeaderText="First Name" SortExpression="firstname" ><HeaderStyle HorizontalAlign="Left" /></asp:BoundField>
<asp:BoundField DataField ="lastname" HeaderText="Last Name"><HeaderStyle HorizontalAlign ="Left" /></asp:BoundField>
<asp:CommandField ShowSelectButton="True" ><ItemStyle Width="50px" /></asp:CommandField>
</Columns>
</asp:GridView>
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
SelectCommand="SELECT [Cart.CartID],[Cart.ProdID],[Cart.email],[Cart.ProdName],[Cart.ProdPrice],[Cart.Quantity],[Cart.Total]
FROM [Cart] INNER JOIN [Customers] ON (Customers.email=@email)">
</asp:SqlDataSource>
</td>
<td valign="top">
<asp:FormView ID="FormView1" runat="server" DataSourceID="SqlDataSource1" DataKeyNames="CartID" Width="373px">
<EmptyDataTemplate >
Please select a customer<br /><br />
</EmptyDataTemplate>
<ItemTemplate >
<asp:Label ID="Label1" runat="server" Text="Cart ID:" Width="100px"></asp:Label>
<asp:TextBox ID="txtCartID" runat="server" ReadOnly="True" Width="200px" Text='<%# Eval("CartID") %>' ></asp:TextBox>

<asp:Label ID="Label2" runat="server" Text="Product ID:" Width="100px"></asp:Label>
<asp:TextBox ID="txtProdID" runat="server" ReadOnly="True" Width="200px" Text='<%# Eval ("ProdID") %>'></asp:TextBox>

<asp:Label ID="Label3" runat="server" Text="Product Name:" Width="100px"></asp:Label>
<asp:TextBox ID="txtProdName" runat="server" ReadOnly="true" Width="200px" Text='<%# Eval("ProdName") %>'></asp:TextBox>

<asp:Label ID="Label4" runat="server" Text="Product Price:" Width="100px"></asp:Label>
<asp:TextBox ID="txtProdPrice" runat="server" ReadOnly="true" Width="200px" Text='<%# Eval ("ProdPrice","{0:C}") %>'></asp:TextBox>

<asp:Label ID="Label5" runat="server" Text="Quantity:" Width="100px"></asp:Label>
<asp:TextBox ID="txtQuantity" runat="server" ReadOnly="true" Width="200px" Text='<%# Eval("Quantity") %>'></asp:TextBox>

<asp:Label ID="Label6" runat="server" Text="Total:" Width="100px"></asp:Label>
<asp:TextBox ID="txtTotal" runat="server" ReadOnly="true" Width="200px" Text='<%# Eval("Total","{0:C}") %>'></asp:TextBox>

</ItemTemplate>
</asp:FormView>
&nbsp;
</td>
</tr>
</table>