503 valid RCPT command must precede DATA on Exchange 2003 using Outlook 2007
Posted on 2008-10-29
Here's an email that came back:
firstname.lastname@example.org on 10/28/2008 2:27 PM There was a SMTP communication problem with the recipient's email server. Please contact your system administrator. <domain.com #5.5.0 smtp;503 valid RCPT command must precede DATA>
after some research it seems that acceptable workaround for this to enable"my server requires authentication" for a pop3 box. however my users are using a exchange server without pop3 connector. i see the following options under Outlook 2007 exchange options> security > network security: negotiate authentication, kerberos, ntlm.
Whats the proper authentication method to fix the issue stated above? sorry this is a live server and I dont want to play test and trial game on this one.