title: 4.4.2 SMTP error from one server
body: <p>My hosting is on a shared server and it all works well,  except for one recurrent email problem.
  client Emails from the UK branch of a bigbusiness get returned  to the sender with a 4.4.2  error. 
  same domain sent from the US or Asia offices are delivered. 
  The host says " not our problem" and the UK branch of bigbusiness.com  say " not our problem - you are the only one that this is happening to "</p>
  
  <p>so what do i do next, and what additional information do i need  to try and have an intelligent conversation with the relevant person (who is ?)  to sort this out . </p>