XCON: Non-Delivery Report Is Generated When SMTP Messages Are Relayed to a Lotus Domino Server

When the Internet Information Server (IIS) Simple Mail Transfer Protocol (SMTP) service is configured to relay SMTP messages to a Lotus Domino R5.x server, the message originator may receive a non-delivery report (NDR) that is similar to the following message:

This issue can occur if the Domino server has not been configured to support 8-bit MIME-formatted messages. When the SMTP service receives an 8-bit MIME-formatted message that needs to be routed to a Domino server, the SMTP service initiates an SMTP connection to the Domino server. After the SMTP service sends an EHLO command, Domino responds with its list of supported ESMTP verbs. If "8BITMIME" is not included in the list of support verbs, the SMTP service cannot deliver the message to the Domino recipient because Domino has not been configured to understand the message format. The SMTP service then sends the RSET command to Domino to reset the SMTP connection. Finally, the SMTP service sends an NDR to the original sender. To view the SMTP commands that are sent, use a network packet analyzer, such as Microsoft Network Monitor.

Top resolve this issue:

1.	On the Domino server, open the server's Configuration Document.
2.	Click the Router/SMTP tab, and then click the Advanced tab. The ESMTP verbs that can be enabled are displayed in the Commands and Extensions section; one of the verbs is "8BITMIME".

To check to see if the Domino server supports a certain extension, telnet to port 25 of the Domino server, and then type EHLO domain.com. You can perform the same telnet procedure against the SMTP service to see a larger set of supported MIME types. The SMTP service cannot down-convert an 8-bit MIME message to 7-bit.