Mailing List Archive: Callback

Callback

May 22, 2002, 8:45 AM

Post #1 of 5 (1581 views)

Hi all,

i've set in my exim.conf host callback:

sender_verify_hosts_callback = *
sender_verify_callback_domains = *

I've noted that exim try to verify incoming mail back to the same host
where have received it...

exim_mainlog:
2002-04-22 09:27:42 16zYEf-0004Fj-00 <= user1@mydomain.it
H=(mail5.cs.interbusiness.it)

exim_rejectlog:

2002-05-20 17:54:22 179pUM-0000jc-00 rejected from
(mail5.cs.interbusiness.it) [151.99.250.40]: temporarily unable to verify
sender address <user1@mydomain.it> (try later)

see DNS mx query:

> qnt.it
Server: ases01.ases.it
Address: 192.168.200.1

Non-authoritative answer:
mydomain.it MX preference = 10, mail exchanger = mail.mydomain.it

mydomain.it nameserver = dns2.nic.it
mydomain.it nameserver = dns.mydomain.it
mail.mydomain.it internet address = x.x.x.x
dns2.nic.it internet address = 193.205.245.8
>

Why exim is calling back the sending host? It should callback host in DNS
MX query....

I can use one mail server for incoming mail and another one for outcoming mail.

Riccardo

Re: Callback [ In reply to ]

djc at microwave

May 22, 2002, 10:22 AM

Post #2 of 5 (1536 views)

Permalink

On Wed, 22 May 2002, Riccardo Baldanzi wrote:

> Hi all,
>
> i've set in my exim.conf host callback:
>
> sender_verify_hosts_callback = *
> sender_verify_callback_domains = *
>
> I've noted that exim try to verify incoming mail back to the same host
> where have received it...
>
> exim_mainlog:
> 2002-04-22 09:27:42 16zYEf-0004Fj-00 <= user1@mydomain.it
> H=(mail5.cs.interbusiness.it)
>
> exim_rejectlog:
>
> 2002-05-20 17:54:22 179pUM-0000jc-00 rejected from
> (mail5.cs.interbusiness.it) [151.99.250.40]: temporarily unable to verify
> sender address <user1@mydomain.it> (try later)
>
> see DNS mx query:
>
> > qnt.it
> Server: ases01.ases.it
> Address: 192.168.200.1
>
> Non-authoritative answer:
> mydomain.it MX preference = 10, mail exchanger = mail.mydomain.it
>
> mydomain.it nameserver = dns2.nic.it
> mydomain.it nameserver = dns.mydomain.it
> mail.mydomain.it internet address = x.x.x.x
> dns2.nic.it internet address = 193.205.245.8
> >
>
> Why exim is calling back the sending host? It should callback host in DNS
> MX query....

What makes you think it is? The log line shows the host the mail was
trying to come from, not the host that it called-back..

>
> I can use one mail server for incoming mail and another one for outcoming mail.
>
> Riccardo
>
>
> --
>
> ## List details at http://www.exim.org/mailman/listinfo/exim-users Exim details at http://www.exim.org/ ##
>
>

--

Re: Callback [ In reply to ]

ph10 at cus

May 23, 2002, 1:03 AM

Post #3 of 5 (1549 views)

Permalink

On Wed, 22 May 2002, Riccardo Baldanzi wrote:

> 2002-05-20 17:54:22 179pUM-0000jc-00 rejected from
> (mail5.cs.interbusiness.it) [151.99.250.40]: temporarily unable to verify
> sender address <user1@mydomain.it> (try later)

> Why exim is calling back the sending host? It should callback host in DNS
> MX query....

It should call back to the host that Exim gets from its routers. That
*may* be from an MX, but it depends on how your routers are configured.
What is the output from "exim -bt user1@mydomain.it" ?

However, that log line doesn't show that a callback failed. All it says
is that it couldn't verify that address. This could be for several
reasons - e.g. it couldn't look up the MX records. 151.99.250.40 is the
*sending* host, not the callback host.

--
Philip Hazel University of Cambridge Computing Service,
ph10@cus.cam.ac.uk Cambridge, England. Phone: +44 1223 334714.

Re: Callback [ In reply to ]

riccardo.baldanzi at libero

May 23, 2002, 1:15 AM

Post #4 of 5 (1539 views)

Permalink

Sorry, my fault....i've activated firewall logging and i saw that exim was
calling back host in DNS MX query.
Unfortunately, in my case, that host was permanently down and so exim is
temporarily unable to verify sender and neither the receiver or the sender
received any error (why?).

I must test more carefully before posting.

Riccardo

At 10.03 23/05/2002, you wrote:
>On Wed, 22 May 2002, Riccardo Baldanzi wrote:
>
> > 2002-05-20 17:54:22 179pUM-0000jc-00 rejected from
> > (mail5.cs.interbusiness.it) [151.99.250.40]: temporarily unable to verify
> > sender address <user1@mydomain.it> (try later)
>
> > Why exim is calling back the sending host? It should callback host in DNS
> > MX query....
>
>It should call back to the host that Exim gets from its routers. That
>*may* be from an MX, but it depends on how your routers are configured.
>What is the output from "exim -bt user1@mydomain.it" ?
>
>However, that log line doesn't show that a callback failed. All it says
>is that it couldn't verify that address. This could be for several
>reasons - e.g. it couldn't look up the MX records. 151.99.250.40 is the
>*sending* host, not the callback host.
>
>
>--
>Philip Hazel University of Cambridge Computing Service,
>ph10@cus.cam.ac.uk Cambridge, England. Phone: +44 1223 334714.

Re: Callback [ In reply to ]

djc at microwave

May 23, 2002, 11:27 AM

Post #5 of 5 (1542 views)

Permalink

On Thu, 23 May 2002, Riccardo Baldanzi wrote:

> Sorry, my fault....i've activated firewall logging and i saw that exim was
> calling back host in DNS MX query.
> Unfortunately, in my case, that host was permanently down and so exim is
> temporarily unable to verify sender and neither the receiver or the sender
> received any error (why?).

Well, if you have enabled callbacks, and you verify the sender address,
and their MX host is permanently shut down, it wont be able to verify
the senders address via callback.

The sender will also be unable to receive any non-delivery notice, if
their MX host is permanently shut down. If you dont have any reason to
beleive otherwise, it was probably a spammers domain, they spammed from
somewhere other than their MX host (dialups, open relay, ...), and the
provider hosting their mail found out and shut them down.

>
> I must test more carefully before posting.
>
> Riccardo
>
> At 10.03 23/05/2002, you wrote:
> >On Wed, 22 May 2002, Riccardo Baldanzi wrote:
> >
> > > 2002-05-20 17:54:22 179pUM-0000jc-00 rejected from
> > > (mail5.cs.interbusiness.it) [151.99.250.40]: temporarily unable to verify
> > > sender address <user1@mydomain.it> (try later)
> >
> > > Why exim is calling back the sending host? It should callback host in DNS
> > > MX query....
> >
> >It should call back to the host that Exim gets from its routers. That
> >*may* be from an MX, but it depends on how your routers are configured.
> >What is the output from "exim -bt user1@mydomain.it" ?
> >
> >However, that log line doesn't show that a callback failed. All it says
> >is that it couldn't verify that address. This could be for several
> >reasons - e.g. it couldn't look up the MX records. 151.99.250.40 is the
> >*sending* host, not the callback host.
> >
> >
> >--
> >Philip Hazel University of Cambridge Computing Service,
> >ph10@cus.cam.ac.uk Cambridge, England. Phone: +44 1223 334714.
>
>
> --
>
> ## List details at http://www.exim.org/mailman/listinfo/exim-users Exim details at http://www.exim.org/ ##
>
>

--