Oracle Developer Tools for Visual Studio

by following code, i want to an Email address to DB, defined to Varchar2. when I got a value by TextBox, for example: input "xxx@hotmail.com",
error like:Unspecified errorORA-04054: database link HOTMAIL.COM does not exist
only if remove "@" the value will be insert successfully, however it is not a standard email address format, how to handle it?

Connect()
        Dim myCommand As New OleDb.OleDbCommand
        myCommand.CommandText = "INSERT INTO register VALUES (" & _
                                "111" & ", " & _
                                "5555555" & ", " & _
                                Me.TextBox2.Text & ") "  
        myCommand.CommandType = CommandType.Text
        myCommand.Connection = myConnection
        Dim myRecAffected As Integer
        Try
            myRecAffected = myCommand.ExecuteNonQuery
            If myRecAffected = 1 Then
                Me.TextBox1.Text = "Successful insertion"
            Else
                Me.TextBox1.Text = "Insertion did not work well"
            End If
            Disconnect()
        Catch ex As Exception
            Me.TextBox1.Text = ex.Message
        End Try

Any help will be appricated!!!