title: Email validation MX Lookup
body: <p>I have been asked to implement some email address validation on a web app - I'm sure we've all been there a thousand times... however, this time I have been asked to do an MX Lookup on the domain to see if it accepts emails.</p>
  
  <p>Does anyone know of any potential problems with doing this? Is an mx lookup a reliable way of finding out if a domain accepts email? are there any edge cases where a valid email address could fail an MX lookup check?</p>
  
  <p>Thanks for your advice! </p>