The parameter 'addresses' cannot be an empty string

I am trying to send an email in ASP.NET using the `System.Net.Mail.SmtpClient` class. However I am getting the following exception message: The parameter 'addresses' cannot be an empty string. Parameter name: addresses This is my send email code: ``` private void SendEmailUsingGmail(string toEmailAddress) { try { SmtpClient smtp = new SmtpClient(); smtp.Credentials = new NetworkCredential("keysketyyyy@gmail.com", "sdsdasd"); smtp.Port = 587; smtp.Host = "smtp.gmail.com"; smtp.EnableSsl = true; MailMessage message = new MailMessage(); message.From = new MailAddress("keysketyyy@gmail.com"); message.To.Add(toEmailAddress); message.Subject = "Write your email subject here"; message.Body = "write the content of the email here"; smtp.Send(message); } catch (Exception ex) { Response.Write("Error occured: " + ex.Message.ToString()); } } ``` The exception is being caught in the `SendEmailUsingGmail` catch block. This is the calling code: ``` protected void Button1_Click(object sender, EventArgs e) { string connStr = ConfigurationManager.ConnectionStrings["mydms"].ConnectionString; SqlConnection mySQLconnection = new SqlConnection(connStr); if (mySQLconnection.State == ConnectionState.Closed) { mySQLconnection.Open(); for (int i = 0; i < Repeater2.Items.Count; i++) { DropDownList DropDownListcontrol = ((DropDownList)Repeater2.Items[i].FindControl("DropDownList4")); Label DocId = ((Label)Repeater2.Items[i].FindControl("DocId")); SqlCommand cmd = new SqlCommand("approveddd", mySQLconnection); cmd.CommandType = CommandType.StoredProcedure; cmd.Parameters.Add("@DocID", SqlDbType.Int).Value = Convert.ToInt32((DocId.Text)); cmd.Parameters.Add("@ApproveID", SqlDbType.Int).Value = Convert.ToInt32(DropDownListcontrol.SelectedValue); cmd.Parameters.Add("@ApproveBy", SqlDbType.VarChar, 50).Value = (Session["Login2"]); try { cmd.ExecuteNonQuery(); string emailId = ((Label)Repeater2.Items[i].FindControl("Label2")).Text; SendEmailUsingGmail(emailId); } catch (Exception ex) { Supvisor.Text=(ex.Message); } cmd.ExecuteNonQuery(); //UPDATE APPPROVEID IN DOCUMENTINFO TABLE //DMSLIB.Doc myDoc = new DMSLIB.Doc(); //myDoc.MarkDocAs(Convert.ToInt16(DocId.Text), Convert.ToInt32(DropDownListcontrol.SelectedValue)); } } else { Supvisor.Text = "Error"; } if (mySQLconnection.State == ConnectionState.Open) { mySQLconnection.Close(); } } ``` When an admin approves / rejects a document the data is saved into database like this: ``` SeqNo DocID ApproveID ApproveBy 82 20 3 john 83 21 1 john 84 18 2 kety 85 19 1 emel ``` I also send an email when admins click a button, the email is sent to respective email ids like this, as I show in a repeater table: ``` DocID DocName Uplaodedfile UserEmail DocType DepType ApproveID 1 ABC def.pdf abcdef@gmail.com pdf hr (In this i set dropdown values are (approve/reject/pending) ```