Knowledgebase
Error : 503 valid RCPT command must precede DATA
Posted by Sam Nexus on 01 July 2006 06:37 AM
If when you try to send mail you are receiving an error with the following message: "503 valid RCPT command must precede DATA" then you need to configure your email client (ie Outlook Express) to authenticate automatically by checking the "my server requires authentication" box in your email configuration.

In most programs this is in Advanced or More Settings and on a Server settings or Outgoing server settings.