Sendmail 8.6.12 problem

Sendmail 8.6.12 problem

Post by Stephen Sout » Thu, 02 Nov 1995 04:00:00



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
sending it.

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
message!

Aaarrgghhh!!!

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:

   nottingham

form. Add so much as a full stop--for example:

   nottingham.

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.

--
Stephen Souter

 
 
 

Sendmail 8.6.12 problem

Post by David B Fu » Fri, 03 Nov 1995 04:00:00




>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
>sending it.
<
>4) Go back to Step 1!

Hmm, that looks like a DNS resolver problem, not sendmail's fault.
Sendmail is heavily dependent upon DNS stuff, so a DNS bug can make
sendmail look sick.

It looks like your DNS resolver library ("res_search") is doing the MX
lookup on the simple name, not finding anything (returning an empty list)
but not setting 'h_errno' to indicate the "Non-existent-domainname" error.
So sendmail sees the lack of MX data and complains accordingly, but since
h_errno == 0 (zero => OK) it doesn't drop it as an invalid name; thus
the infinite retry.

My guess is that you need a newer (or better) DNS resolver library for your
system. What revision of DNS does it have?
That -or- the resolver lib revision does NOT match the revision of the
"resolv.h" include file that you used when you built sendmail. EG: somebody
installed BIND-4.9.x but you still have the v-4.8.3 resolv.h include file.

PS: one other possible source of this kind of problem is a wild-card MX
record in your DNS zone (bad news) or some other kind of DNS server problem.
However I checked your DNS and it looks OK, so I'm going to assume that you
don't have a BIND problem. You still might want to check this further.

--

Sys-admin/News-admin/Postmaster for ICAEN
Better is not better, 'standard' is better. B{
#include <std_disclamer.h>

 
 
 

Sendmail 8.6.12 problem

Post by Jim Jagiels » Sat, 04 Nov 1995 04:00:00




>>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)
>Yes, I think so. I've seen the same problem a number of versions of sendmail,
>most recently with 8.7.1.
>The problem appears to stem from the resolver returning 0 on queries of the type
>you describe.  What I did, and what appears to have solved the problem was to
>add the BROKEN_RES_QUERY define intended for OSF systems to the AUX definitions
>in conf.h.

Ummm...

The actual define is BROKEN_RES_SEARCH and, in conf.h, it already _is_
defined for A/UX.
--
#include <std/disclaimer.h>

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Sendmail 8.6.12 problem

Post by Stephen Sout » Sat, 11 Nov 1995 04:00:00




> Hmm, that looks like a DNS resolver problem, not sendmail's fault.
> Sendmail is heavily dependent upon DNS stuff, so a DNS bug can make
> sendmail look sick.

> It looks like your DNS resolver library ("res_search") is doing the MX
> lookup on the simple name, not finding anything (returning an empty list)
> but not setting 'h_errno' to indicate the "Non-existent-domainname" error.
> So sendmail sees the lack of MX data and complains accordingly, but since
> h_errno == 0 (zero => OK) it doesn't drop it as an invalid name; thus
> the infinite retry.

> My guess is that you need a newer (or better) DNS resolver library for your
> system. What revision of DNS does it have?
> That -or- the resolver lib revision does NOT match the revision of the
> "resolv.h" include file that you used when you built sendmail. EG: somebody
> installed BIND-4.9.x but you still have the v-4.8.3 resolv.h include file.

If this is the case, will there be a fix in the next version of BIND/DNS?

Since nobody has mentioned it, I take it the problem (assuming DNS *is*
the villain) has not (yet) been addressed in the beta version of the new
BIND/DNS available from Jagubox?

BTW, as to the problem itself, one of the people at our site suggested
this as a "fix", to be added to the end of RuleSet 96 in the sendmail.cf
file:



a Host Unknown errors occurs in place of the Operating System error,
allowing sendmail to dispose of the errant message in a friendlier
fashion.

It seems to work, but I hesitate to call such a kludge a "fix". Can
anybody offer a more elegant solution?

--
Stephen Souter

 
 
 

Sendmail 8.6.12 problem

Post by Brad Knowl » Sun, 12 Nov 1995 04:00:00






> > My guess is that you need a newer (or better) DNS resolver library for your
> > system. What revision of DNS does it have?
> > That -or- the resolver lib revision does NOT match the revision of the
> > "resolv.h" include file that you used when you built sendmail. EG: somebody
> > installed BIND-4.9.x but you still have the v-4.8.3 resolv.h include file.

> If this is the case, will there be a fix in the next version of BIND/DNS?

If the problem is as Dave suspects, then it's your problem and not
something that BIND can fix for you -- you'll need to remove the 4.8.3
stuff yourself, because whomever did the BIND installation didn't complete
the job.

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