private void btn_GetHeaders_Click(object sender, EventArgs e) { ImapClient client = new ImapClient("imap.gmail.com", 993, txt_Email.Text, txt_Password.Text, AuthMethod.Auto, true); IEnumerable <uint> uids = client.Search(SearchCondition.Answered()); listBox1.Items.Clear(); listBox1.Items.Add("Now you see ' Answered ' mails "); foreach (var item in uids) { listBox1.Items.Add(item); } }