We run Sendmail 8.6.12 (using Apple A/UX 3.1.1 on an Apple WorkGroup
Server 95) at our site.
We have had version 8.6.12 up and running for only the past few months,
and three times now we have struck a particularly annoying problem when
people try sending email to an address like:
Obviously such a sitename is an invalid Internet address, but that's
beside the point. What appears to happens next is this
1) Sendmail can't deliver the mail, so it generates a session with a
transcript that looks (in part) like this:
554 getmxrr: res_search (nottingham) failed with impossible h_errno (0)
2) It next shoots off a complaint to both the sender & the postmaster (me).
3) Instead of being deleted, the original message stays in the mail queue.
A few hours later, a dutiful Sendmail takes notice and has another go at
4) Go back to Step 1!
The first time this happened, I was away on leave for a week. When I came
back I found my email postbox stuffed to the gills with four or five
hundred complaints from the Mailer Daemon, all generated by just one email
I have since run a few tests, and so far as I can make out it *only*
happens when the site name is in the:
form. Add so much as a full stop--for example:
and you just generate a "Host Unknown" error and the message politely
vanishes from the mail queue.
Getting rid of these troublemakers is simple enough: delete them from the
queue. But that does not help the larger problem of why it should happen
at all. (It never happened once with the old version of sendmail we ran,
and we were using that for the better part of 18 months.)
Is it merely a configuration bug causing this or is there a problem with
this version of sendmail itself?
And is there a fix?
(Bearing in mind that Sendmail does retain messages in the queue under
other circumstances (eg when the destination host is "unreachable"), would
I be wrong in thinking this looks suspiciously like Sendmail mistakening
invoking a "feature" to deal with the problem instead of tossing out the
offending message entirely?)
Thanks in advance.