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Connection debug

 

 

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towern at gmail

Oct 21, 2009, 3:56 AM

Post #1 of 4 (614 views)
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Connection debug

Hi

How can I debug connection problem between my exim server and some
machine (scaner, printer, fax) which have mail client on board? I must
do it safely because i have about 5000 clients working online on that
server. Would be fine if i could start a separate exim process.

Logs tell nothing, so i must use some tool.

Regards!

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fh-exim2003 at lf

Oct 21, 2009, 4:06 AM

Post #2 of 4 (579 views)
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Re: Connection debug [In reply to]

On Wed, Oct 21, 2009 at 12:56:47PM +0200, tower wrote:
> Hi
>
> How can I debug connection problem between my exim server and some
> machine (scaner, printer, fax) which have mail client on board? I must
> do it safely because i have about 5000 clients working online on that
> server. Would be fine if i could start a separate exim process.
>
> Logs tell nothing, so i must use some tool.

you could try using a packet-sniffer like tcpdump or wireshark
to read the SMTP handshake.

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Regards
Frank

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mike at pellatt

Oct 21, 2009, 4:18 AM

Post #3 of 4 (582 views)
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Re: Connection debug [In reply to]

On 21/10/09 11:56, tower wrote:
> Hi
>
> How can I debug connection problem between my exim server and some
> machine (scaner, printer, fax) which have mail client on board? I must
> do it safely because i have about 5000 clients working online on that
> server. Would be fine if i could start a separate exim process.
>
> Logs tell nothing, so i must use some tool.
>
>
Err, ping, traceroute, telnet and wireshark?? If it's a connection
problem, those should be all the tools you need to identify where the
problem is.

If it's a data transfer/protocol problem, rather than a connection
problem, then a bit more info would help identify the best tool for the job.

If the connection is succeeding but the message isn't getting
transferred, run exim in debug mode on that message. How to do it is all
in the docs, but it's not the sort of detail I carry about in my brain
with its ever-diminishing storage capacity.

Mike Pellatt
Who is apparently too old to work for a hosting company. I should prefer
to be putting my feet up. Really.

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exim-users at spodhuis

Oct 21, 2009, 11:50 AM

Post #4 of 4 (572 views)
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Re: Connection debug [In reply to]

On 2009-10-21 at 12:56 +0200, tower wrote:
> How can I debug connection problem between my exim server and some
> machine (scaner, printer, fax) which have mail client on board? I must
> do it safely because i have about 5000 clients working online on that
> server. Would be fine if i could start a separate exim process.
>
> Logs tell nothing, so i must use some tool.

You can add stuff to Exim's logging with the "log_selector"
configuration in the main section. If you just use "+foo" for each item
you add, then you're adding to what's logged. You might want:

log_selector = +smtp_connection +smtp_incomplete_transaction \
+smtp_no_mail +smtp_protocol_error +smtp_syntax_error

With those, you can see if the device is connecting to Exim. It should
be a low-risk change to your config. You can use:
exim -C /path/to/different/config -bV
to do some basic checks before putting the new config live.

If, after adding +smtp_connection to log_selector, you still get
nothing, then the problem lies outside Exim.

If you want to get full debugging of a connection from a particular IP,
then what I'd do is:

(1) Run a debug Exim on a different port:
# exim -d -oX 26 -bd
(2) Use the host packet filter to do a port redirection for traffic
from a particular host; any modern packet filter should be capable
of doing this.

If you need more information on a particular aspect of Exim, check the
documentation on the different sub-options for -d; eg:
# exim -d+expand+acl+auth -oX 26 -bd

With PF packet filtering, you'd use something like:

rdr on ne0 inet proto tcp from 192.0.2.30 to port 25 -> 192.0.2.4 port 26

if your mail-server is on [192.0.2.4], the network device is ne0 and you
want to get debugging info for SMTP connections from [192.0.2.30].

There will be something equivalent for iptables on Linux, I'm sure.

-Phil

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