We have got a website that sends an e-mail to a person that wants to become a member to verify if they are who they say they are. For one reason or another 90% of the e-mail send to a hotmail account is returned to us with a smtp;500 Syntax error, all other providers have no problem. Until a few weeks ago everything worked perfect. and now it is a bit of a mess. Has somebody an idea of the problem and better yet of the solution?