Last week I moved the server that hosts this Web site. Ever since then, I've been getting a very strange error whenever the server tries to send email. Here's a sample:

Jun 13 14:21:27 lynx sendmail[14437]: j5DKLQ7I014435:
to=, ctladdr= (0/0),
delay=00:00:00, xdelay=00:00:00, mailer=esmtp, pri=30303,
relay=windley.org, dsn=5.1.2, stat=Host unknown (Name server:
windley.org: no data known)

Googling the error message, ("no data known") was almost no help at all. Seems lots of people have seen that error, but no one knows how to fix it. In general, it means that sendmail couldn't get DNS information for the host. But, running "host -tANY windley.org" at the command line showed that the DNS information was available and correct.

I finally solved the problem by changing the line

C{w}localhost.localdomain

in my sendmail.cf file to

C{w}lynx.windley.net

This solved the problem. Now, I'm sure there are all kinds of reasons why having my sendmail.cf file misconfigured caused this problem, but the more interesting thing to me is that this worked fine for more than a year at the old place. The new environment that the server found itself in is what "broke" it. This just points out how brittle system configurations are.