Such an error can be returned immediately in response to an address provided to PMDF through a user agent, or the error can be deferred and returned as part of an error return mail message. In all cases, such an error message indicates that PMDF is not able to deliver mail to the specified host. Before diagnosing such problems any further, verify that the address in question is indeed correct and is not misspelled, transcribed incorrectly, or using the name of a host or domain which no longer exists.
Try running the address in question through the
-rewrite utility. If this utility also returns an "illegal
host/domain" error on the address, then PMDF has no rules in its
pmdf.cnf and related files, to handle
the address. Verify that you have configured PMDF correctly, that you
answered all configuration questions appropriately, and that you have
kept your configuration information up to date.
pmdf test -rewrite does not encounter an
error on the address, then PMDF was able to determine how to handle the
address, but the network transport would not accept it. You can examine
the appropriate log files from the delivery attempt for additional
details. Transient network routing or name service errors should not
result in returned error messages, though it is possible for badly
misconfigured domain name servers to cause such problems.
If you are on the Internet then check that you have properly configured your TCP/IP channel to support MX record lookups. Many domain addresses are not directly accessible on the Internet and require that your mail system correctly resolve MX entries. If you are on the Internet and your TCP/IP is configured to support MX records, you should have allowed the PMDF configuration utility to enable MX support; see Chapter 23. If your TCP/IP package is not configured to support MX record lookups, then you will not be able to reach MX-only domains.