title: Relay access denied, system.net.mail
body: <p>We have a aspx.net site which send out mail to users using a web server hosted externly.</p>
  
  <p>This have been working perfectly for a couple of years sending 100-1000 mails pr day, but recently users have started to report that they do not recieve mails - some days they recieve all mails (2-100) and some days only 40-60%. </p>
  
  <p>All mails are formatted equal and have the same content (except for some dynamic fields like name, password etc).</p>
  
  <p>I've looked at my error log and now I see this error when mails are lost:</p>
  
  <pre><code>system.net.mail.smtpexception: transaction failed the server response was: &lt;name@domain.tld&gt; Relay access denied
  </code></pre>
  
  <p>Any feedback would be appriciated.</p>
  
  <p>Regards and happy coding,
  Thomas</p>