private void button1_Click(object sender, EventArgs e)
        {
            string[] gmail = GetGmails(txtGmail.Text);
            for (int i = 0; i < gmail.Count(); i++)
            {
                gmail[i] += "@gmail.com";
            }
            txtEmail.Lines = gmail;
        }

        /// <summary>
        /// Gets a list of all possible dot tricked gmails.
        /// </summary>
        /// <param name="acc">The account name without @gmail.com.</param>
        /// <returns>All the possible doted gmails without @gmail.com</returns>
        public string[] GetGmails(string acc)
        {
            if (acc.Length > 1 && acc.Length < 31)
            {
                string head = acc.Substring(0, 1);
                string tail = acc.Substring(1, acc.Length - 1);
                string[] tails = GetGmails(tail);
                string[] ret = new string[tails.Length * 2];
                int iRet = 0;
                foreach (string t in tails)
                {
                    ret[iRet] = head.ToString() + t;
                    iRet++;
                    ret[iRet] = head.ToString() + '.' + t;
                    iRet++;
                }
                return ret;
            }
            else
            {
                string[] ret = { acc };
                return ret;
            }
        }