Re: [exim] sender verify callout to non smtp source

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Author: Dermot Paikkos
Date:  
To: Russell King
CC: Exim-users
Subject: Re: [exim] sender verify callout to non smtp source
the error message, by the way was:

   mail.example1.com [ipadd]: 451-could not connect to
     weblive-01.mysite.co.uk [ipadd]: No route to host\r
    451-Could not complete sender verify callout for\r
    451-<nobody@???>.\r 451-The mail server(s) 
        for the domain may be temporarily unreachable, or\r 451-they may 
be permanently unreachable from this server. In the latter case,\r
     451-you need to change the address or create an MX record for             
    its domain\r 451-if it is supposed to be generally accessible        
    from the Internet.\r 451 Talk to your mail administrator for               
  details.: retry timeout exceeded


On 9 Mar 2005 at 10:24, Russell King wrote:

> > Our web site (externally hosted) uses a plugin to send emails to
> > clients. One client's server (exim 4.34) is rejecting the mails with
> > a sender verify message. From my understanding of it, with sender
> > verify the server does a callout to the sending host. Is that
> > correct?


> It does a callout verification against the MX servers for the domain
> of the envelope sender.


I thought that it would query the sending host as it would already
have the ip address for that host so it would presumabley be quickier
to respond directly to them rather than to a dnslookup. Also from the
section on callout verification:

"One way this can be done is to make an SMTP callback to the sending
host (for a sender address)"

Which seemed to imply that it would call back the incoming host.

In this case the return-path was
Return-path: <nobody@???>
but the sender was
From: kevin.davis@???

i imagine this isn't considered good practise.

> > In this case the server will not respond as it isn't a smtp server.
> > Does anyone have any ideas on how to get around this? From my reading
> > of the docs an mx record for that hosts will not work as it will call
> > the sending host only.
>
> There is only one solution. Use a valid envelope sender address.
>
> If you're sending mail from user@???, then not
> only are you sending from an address which is non-returnable, but
> you're also not conforming to generally accepted RFCs, which (eg)
> indicate that postmaster@that domain must work.


This makes alot of sense. The return-path host has now been given a
mx record. The user was nobody. I need to check that that all
resolves corerctly.

> It sounds like you need to tweak your plugin configuration to set
> the sender address appropriately.


yes we need to do that.
Thanx. I can't really test this as I need the user to place an order
before the mails will go out.
> Russell King


PS: I have another question about to go on the same subject - stay
tune.