[GRLUG] Postfix Error info

[megadave]

Do you know the IP address of the sender host? Does it show in the logs?
Have you checked to see if it has a PTR record, with a matching A record?

Does postfix log the "HELO" argument sent by the sending server? What is
it? Does it contain only valid characters?

I use Exim. If it rejects a host, it clearly shows the IP address of the
rejected server, as well as the specific configured reason it was rejected,
wether thts based on IP address, remote hostname, sender address or domain,
etc). It shows the HELO name given by the server.

If it is configured to check matching forward/reverse DNS, if it finds a
mismatch, it clearly logs the specific host name and IP address which it
finds to mismatch. It can even be configured to log the individual lines of
the SMTP connection (HELO/EHLO, MAIL FROM, RCPT TO) as well as its
responses, as well as the full headers of messages rejected after "DATA",
if desired (this can be per-sender-host, if needed for intensive debugging)

I can even "fake" a connection from a specified IP address, and see what
checks it is processing as it performs them, and see if/where it fails a
check, based on what information.






On Tue, Sep 10, 2013 at 12:09 PM, L. V. Lammert <lvl at omnitec.net> wrote:

> On Tue, 10 Sep 2013, megadave wrote:
>
> > Well, I wouldnt say "send a postfix error" to the sender.  I would use
> the
> > error message to determine what the problem is. (eg, "your hostname has
> no
> > DNS record", or "your hostname has an illegal character", etc) and then
> > tell them THAT.
> >
> "Invalid Hostname" or "Hostname not found" is tantamount to a Postfix
> error, .. "your hostname has no DNS record" may, or may not be a cause. It
> could be a "_", as mentioned, .. it could be no reverse DNS, ,.. it could
> be no MX record (!!), ..
>
> That's why I am looking for more definitive reasons FOR the erros that
> Postfix throws.
>
> > Perhaps there is some documentation for postfix that might explain what
> > that error means. I am used to SMTP servers that give specific
> information
> > when they log an error that identifies exactly what the cause is.
> >
> What sort of SMTP servers and sample errors? I have used Sendmail &
> Postfix, and the errors have always been similar to the ones mentioned.
>
> > I'm assuming you've done the basics and verified that the sender is
> sending
> > to the correct address, and that their email client is properly
> configured
> > with their valid sender address. Do you know if your server rejects ALL
> > mail from this sending server, or just from this one user?
> >
> The server is being rejected, ..
>
> > If you'd like to get more information about the SMTP transaction from
> this
> > problematic sender, I could setup a temporary address on a server under
> my
> > control, and you could have your sender attempt to email it. If mine
> > rejects it, I would be able to tell you exactly why.  If it accepts it, I
> > may be able to provide details about the transaction that might help you
> > identify why your server is rejecting it.
> >
> As could I - what SMTP are you using that provides specific errors if not
> sendmail, Postfix, or perhaps smptd?
>
>         Lee
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