<a class="btn btn-sm blue" data-toggle="dropdown">
  <i class="fa fa-gear"></i>
  <i class="fa fa-angle-down "></i>
</a>

//*[@id="grdEmails"]/table/tbody/tr[1]/td[8]/div/a

driver.Manage().Timeouts().ImplicitlyWait(TimeSpan.FromSeconds(10));
IWebElement btnAction = driver.FindElement(By.ClassName("btn btn-sm blue"));
btnAction.Click();

driver.findElement(By.cssSelector("a[class='btn btn-sm blue']"));

driver.findElement(By.xpath("//a[contains(@class, 'btn') and contains(@class, 'btn-sm') and contains(@class, 'blue')]"));