XFOR: Non-Delivery Report with "501 Sender Domain Must Exist" Message (280118)


The information in this article applies to:

  • Microsoft Exchange Server 5.5
This article was previously published under Q280118

SUMMARY

Some Microsoft Exchange e-mail messages generate a non-delivery report (NDR) with the message "501 sender domain must exist." This behavior occurs because the sender domain is not registered on the Internet. Check with your Internet service provider (ISP) or Domain Name System (DNS) administrator to verify that the sender's domain has MX records on the Internet.

MORE INFORMATION

Some other (non-Exchange Server) mail systems check the sender's e-mail domain to prevent junk e-mail (spam). This is called performing a reverse lookup.

When these mail systems receive an SMTP connection, they attempt name resolution based on the address in the From field. If the address in the From field cannot be resolved by DNS, the receiving mail system responds with "501 Sender domain must exist," and closes the connection, causing the NDR.

As a test, try to telnet the destination server over port 25. You receive the following results

mail from:test@DomainTest.com
501 test@DomainTest.com... Sender domain must exist

and the connection generates the NDR.

Then, try opening a telnet session over port 25 from a domain that is known to work. The following results are returned:

mail from:test@Microsoft.com
250 test@Microsoft.com... Sender ok

Modification Type:MinorLast Reviewed:4/25/2005
Keywords:kbinfo KB280118
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