I've been having problems with getting Exchange 2007 to allow anonymous/unauthenticated SMTP clients on another computer on the network to send mail. I've followed the article on the Exchange team blog here: http://msexchangeteam.com/archive/2006/12/28/432013.aspx I took the second option which grants Anonymous Users permission to send mail to that connector from an IP range (with the range set to the IP addresses of the SMTP client computer which is a web application server). I then took the last step which was to open up PowerShell and execute this command: Get-ReceiveConnector "External Relay" | Add-ADPermission -User "NT AUTHORITY\ANONYMOUS LOGON" -ExtendedRights "ms-Exch-SMTP-Accept-Any-Recipient" But even after doing this I keep getting 5.1.7 Unable to Relay whenever I telnet into the Exchange server on port 25 from the client computer and attempt to send an email to an address outside of the organisation, this happens regardless of whatever address is used as the MAIL FROM value. But here comes the very strange part:PHP is configured on the application server to send mails sent from the mail() function to the Exchange server on port 25, no special settings are set. Emails sent that way correctly arrive at the destination off-domain mailbox no matter what the from address....but messages sent via Telnet on port 25 fail, as do messages sent by ASP.NET's System.Net.Mail.SmtpClient.Send, they both get the 5.1.7 Unable to Relay treatment.Just what is going on here?

Hello,Did you check after restarting Transport service?Amit Tank | MVP - Exchange | MCITP:EMA MCSA:M | http://ExchangeShare.WordPress.com

After restarting the server the Transport service was stopped, even though it was set to Automatic.Overlooking this after I restarted the Transport service I still got 5.7.1 Unable to Relay.which is odd, because now it's 5.7.1 and not 5.1.7

So, you have your permissions set to Anonymous, you have your authentication set to TLS and Externally Secured right?The next question is what IP addresses are you allowing to connect to the receive connector? Did you specify all the IP addresses related to the server? in some cases if a server has multiple IP addresses it may try to connect with any of those IP addresses.The other question is what are you trying to relay? Have you tried to deploy wireshare on your 07 Hub server an watch the packets from the source IP address to see what is happening? Any Firewalls between the two servers that may prevent traffic via port 25? BP

Hi,How did you send the email by using Telnet? Did you use the ehlo to do the authentication?Please refer to the below article to check this issue:http://www.computerperformance.co.uk/exchange2003/exchange2003_SMTP_Auth_Login.htmThanksAllen