[9fans] strange mail problems

[9fans] strange mail problems

[Robert Raschke]

Hi,

after a recent pull (I think it was on Monday, but it might actually
be completely incidental, I don't know yet) I have started to get some
problems with receiving mail from one of the mailing lists I subscribe
to.  The errors in the smtpd log look like this:

prunelle Jan 26 08:59:29 [bazar2.conectiva.com.br/200.140.247.68] bazar2.conectiva.com.br!lua-bounces -> tombob.com!rrlua sendercheck: deferred: smtp ping: smtp: dns: dns failure (/net/tcp!bazar2.conectiva.com.br)

The dns failure is coming from validatesender, which I thought was
only executed if verifysenderdomain is on in the stmpd.conf.  But
looking at the source of smtpd, it looks as if validatesender always
gets executed, regardless of smtpd.conf or the -r option to smtpd.

I don't understand the dns failure though, as it is clearly resolving
as is shown in the log entry (200.140.247.68).  What else could be the
reason for such a failure?

Thanks,
Robby

Re: [9fans] strange mail problems

[Richard Miller]

> The dns failure is coming from validatesender, which I thought was
> only executed if verifysenderdomain is on in the stmpd.conf.  But
> looking at the source of smtpd, it looks as if validatesender always
> gets executed, regardless of smtpd.conf or the -r option to smtpd.

validatesender is different from verifysenderdomain: it makes an SMTP
connection and sends a "RCPT TO:" command to check whether the sender
email address actually exists.  To turn this off, you have to delete
or rename the /mail/lib/validatesender script.

-- Richard

Re: [9fans] strange mail problems

[Robert Raschke]

Richard wrote:
>> The dns failure is coming from validatesender, which I thought was
>> only executed if verifysenderdomain is on in the stmpd.conf.  But
>> looking at the source of smtpd, it looks as if validatesender always
>> gets executed, regardless of smtpd.conf or the -r option to smtpd.
> 
> validatesender is different from verifysenderdomain: it makes an SMTP
> connection and sends a "RCPT TO:" command to check whether the sender
> email address actually exists.  To turn this off, you have to delete
> or rename the /mail/lib/validatesender script.

OK, that solves the immediate problem, thnak you.

I am seeing very strange dns problems though and I am unsure how to go
about finding what might be wrong with my setup:

cpu% upas/smtp -p /net/tcp!bazar2.conectiva.com.br /dev/null lua-bounces
smtp: dns: dns failure (/net/tcp!bazar2.conectiva.com.br)
cpu% ndb/csquery
> tcp!bazar2.conectiva.com.br!smtp
/net/tcp/clone 200.140.247.68!25
> 
cpu% upas/smtp -p /net/tcp!bazar2.conectiva.com.br /dev/null lua-bounces
cpu% 

[...wait a couple of minutes...]

cpu% upas/smtp -p /net/tcp/clone bazar2.conectiva.com.br /dev/null lua-bounces
smtp: dns: dns failure (/net/tcp/clone)
cpu% 

I seem to keep on losing some information somewhere.
Where would I look to figure this out?

Thanks,
Robby

Re: [9fans] strange mail problems

[Richard Miller]

> I am seeing very strange dns problems though and I am unsure how to go
> about finding what might be wrong with my setup:

If you 'echo debug >/net/dns' it will turn on (or off) verbose debugging
into /sys/log/dns which might give you more information.

I've found that there are fewer intermittent dns failures if you make sure
some of the root servers are in the database to act as a fallback (see
/lib/ndb/local.complicated).

-- Richard