SMTP virtual server sends to external not internal addresses

[amking]

We are using the default microsoft SMTP virtual server to send email messages via IIS. These messages go out to external addresses fine. But they do not get delivered successfully to any addresses inside our domain. Server is running Windows Server 2003. Any help you can provide would be greatly appreciated! Thanks!

Andy

 

[Noway2]

Have you been able to look at any of the error logs to see what is happening. The SMTP protocol specifies number of handshaking steps that describe the process of sending the messages.

Basically, your smtp server will connect to the next SMTP server. This can either be the receiving server or the next hop along the path. When this happens, a HELO process will occur, possibly with an authentication step and then the sending message will say that it has "mail to" a specific user. At this point, if the recipient is deemed valid, the receiving SMTP server should give the go ahead for the message transmission.

Given that outgoing messages are transmitted, it sounds like there is an issue when the (receiving) SMTP server recognizes the recipient as being one of its own. What you will need to figure out is on these cases whether the messages are being accepted and not delivered or if they are being rejected. It could be that the messages are getting accepted, but the local delivery is incorrect.

 

[amking]

The email vendor that we are sending messages to is not able to see the messages hit their incoming mail server at all. I initially thought this was a safelist issue on the incoming mail server, but apparently, we aren't getting those internal domain messages that far yet.

Andy

 

[Noway2]

Look VERY closely at all of the logs. It sounds like some sort of authentication issue. Perhaps them originating email server is appending a prefix or suffix, which is sometimes done to correct FQDNs (fully qualified domain names). For example, if your server is server1.domain, it may be sending things as mail.server1.domain, rendering the addressing invalid.

Also keep this important fact in mind: the email address in the header is irrelevant and is ignored. The recipient and sender information that is communicated through the SMTP transaction is what matters!