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sendind email to an intermittently connected host
I have two hosts a.example.com and p.example.com .
mail for example com arrive to A, but for some users is forwarded to
user@p.example.com .
Nothing special until here, you do with a procmail option at user level.
The problem is that host p could be disconnected, sometime also for
weeks, or even if conencted could refuse messges..
Normally if you forward to a disconnected host after some time (one day ?)
you get a messge telling that you cannot connect it and after some days
gives up and bounces the message, and do it immediately if it get a 5xx
error.
What i want to do is that when sending a message to p.example.com whatever
thing happens (no route to host/ dns error / no response / closed port /
4xx or 5xx error), anything different than an accepted message, the
message remains in the queue and is tried again every 24 hours, indefinitely.
What is easier way ?

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Leonardo Boselli
tel:+393488605348



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Re: sendind email to an intermittently connected host [ In reply to ]
On 17/01/2022 22:56, Leonardo Boselli via Exim-users wrote:
> What i want to do is that when sending a message to p.example.com whatever thing happens (no route to host/ dns error / no response / closed port / 4xx or 5xx error), anything different than an accepted message, the message remains in the queue and is tried again every 24 hours, indefinitely.

That's just a retry rule, for Exim.
There's a docs chapter on retries.
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Cheers,
Jeremy

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Re: sendind email to an intermittently connected host [ In reply to ]
On Mon, 17 Jan 2022, Leonardo Boselli via Exim-users wrote:

> I have two hosts a.example.com and p.example.com .
> mail for example com arrive to A, but for some users is forwarded to
> user@p.example.com .
> Nothing special until here, you do with a procmail option at user level.
> The problem is that host p could be disconnected, sometime also for weeks, or
> even if conencted could refuse messges..
> Normally if you forward to a disconnected host after some time (one day ?)
> you get a messge telling that you cannot connect it and after some days gives
> up and bounces the message, and do it immediately if it get a 5xx error.
> What i want to do is that when sending a message to p.example.com whatever
> thing happens (no route to host/ dns error / no response / closed port / 4xx
> or 5xx error), anything different than an accepted message, the message
> remains in the queue and is tried again every 24 hours, indefinitely.
> What is easier way ?

As Jeremy says, a retry rule will do that.

In addition, there are ways to get p.example to tell a.example that
it would like to receive any waiting messages.
Off the top of my head I don't remember whether the messages come down the
same connectionas the request or a new one, or whether both are possible.


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Andrew C. Aitchison Kendal, UK
andrew@aitchison.me.uk

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Re: sendind email to an intermittently connected host [ In reply to ]
On Tue, Jan 18, 2022 at 1:59 AM Leonardo Boselli via Exim-users <
exim-users@exim.org> wrote:

> I have two hosts a.example.com and p.example.com .
> mail for example com arrive to A, but for some users is forwarded to
> user@p.example.com .
> Nothing special until here, you do with a procmail option at user level.
> The problem is that host p could be disconnected, sometime also for
> weeks, or even if conencted could refuse messges..
> Normally if you forward to a disconnected host after some time (one day ?)
> you get a messge telling that you cannot connect it and after some days
> gives up and bounces the message, and do it immediately if it get a 5xx
> error.
> What i want to do is that when sending a message to p.example.com
> whatever
> thing happens (no route to host/ dns error / no response / closed port /
> 4xx or 5xx error), anything different than an accepted message, the
> message remains in the queue and is tried again every 24 hours,
> indefinitely.
> What is easier way ?
>
> --
> Leonardo Boselli
> tel:+393488605348
>
>
Hi Leonardo,

If I were you, I'd approach the problem a different way. I remember doing
something like that with intermittently connected hosts.
I would instead just queue the messages and let p.example.com to request
for their delivery when its connection comes up.

Please refer to this link for the details:
https://plonk.de/sw/odmr/index.php


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Best regards,
Odhiambo WASHINGTON,
Nairobi,KE
+254 7 3200 0004/+254 7 2274 3223
"Oh, the cruft.", egrep -v '^$|^.*#' :-)
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Re: sendind email to an intermittently connected host [ In reply to ]
On Tue, 18 Jan 2022, Odhiambo Washington via Exim-users wrote:
> If I were you, I'd approach the problem a different way. I remember doing
> something like that with intermittently connected hosts.
> I would instead just queue the messages and let p.example.com to request
> for their delivery when its connection comes up.

No, my situation is different: the p machine normally is connected, but
for some reason, can be unconnected for extended (days to weeks) periods
of time, or ever, more likely, to have the smtp service unactive, or even
just refusing email from certain domains.
But when active it must receive all messages in real time, because among
the services it is used to send notifications to a paging system.

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Leonardo Boselli
tel:+393488605348



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Re: sendind email to an intermittently connected host [ In reply to ]
On Tue, Jan 18, 2022 at 3:10 PM Leonardo Boselli via Exim-users <
exim-users@exim.org> wrote:

> On Tue, 18 Jan 2022, Odhiambo Washington via Exim-users wrote:
> > If I were you, I'd approach the problem a different way. I remember doing
> > something like that with intermittently connected hosts.
> > I would instead just queue the messages and let p.example.com to request
> > for their delivery when its connection comes up.
>
> No, my situation is different: the p machine normally is connected, but
> for some reason, can be unconnected for extended (days to weeks) periods
> of time, or ever, more likely, to have the smtp service unactive, or even
> just refusing email from certain domains.
> But when active it must receive all messages in real time, because among
> the services it is used to send notifications to a paging system.
>

I still believe that it's better to solve the problem from the source -
where the connectivity is almost unpredictable.
You can run the dequeuing process every 5 minutes from p.example.com. That
is quite 'realtime' to me :-)


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Best regards,
Odhiambo WASHINGTON,
Nairobi,KE
+254 7 3200 0004/+254 7 2274 3223
"Oh, the cruft.", egrep -v '^$|^.*#' :-)
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Re: sendind email to an intermittently connected host [ In reply to ]
On 18 Jan 2022, at 11:56, Leonardo Boselli via Exim-users <exim-users@exim.org> wrote:
> No, my situation is different: the p machine normally is connected, but for some reason, can be unconnected for extended (days to weeks) periods of time, or ever, more likely, to have the smtp service unactive, or even just refusing email from certain domains. But when active it must receive all messages in real time, because among the services it is used to send notifications to a paging system.

Lookup up ETRN here:

https://www.exim.org/exim-html-current/doc/html/spec_html/ch-smtp_processing.html (section 8)

Basically, fo all mail destined for that machine you have infinite retry rules according to your own requirements (so the messages never time out or error as undeliverable), and when the far end connects up it makes an ETRN command which then dequeues all the email.

It requires the far end machine to support ETRN, mind you.

Graeme
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Re: sendind email to an intermittently connected host [ In reply to ]
On Tue, 18 Jan 2022, Odhiambo Washington wrote:
> I still believe that it's better to solve the problem from the source -
> where the connectivity is almost unpredictable.

log time unconnections are predictable, since does not occour by a
failure, but intentionally, and system manager for both systems is the
same. so when system return active the unqueuing can be triggered
manually.
And the problem is not for 5 minutes (that BTW is NOT enough realtime
for one of the the needs) but when it is off/inactive/refusing for up to 3
months, when the other system must queue without giving even the slightest
warning.

> You can run the dequeuing process every 5 minutes from p.example.com. That
> is quite 'realtime' to me :-) 

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Leonardo Boselli
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Re: sendind email to an intermittently connected host [ In reply to ]
Am 18.01.22 um 12:02 schrieb Odhiambo Washington via Exim-users:
> Hi Leonardo,
>
> If I were you, I'd approach the problem a different way. I remember doing
> something like that with intermittently connected hosts.
> I would instead just queue the messages and let p.example.com to request
> for their delivery when its connection comes up.
>
> Please refer to this link for the details:
> https://plonk.de/sw/odmr/index.php
>

You mean someting like a message box, that gets pulled from p-server
when it gets online. Some office mailserver do this, so there is
matching configs and software available.

IMHO, sounds like the better option, because messing it's save in the
mailbox, can be accessed from anywhere else and is available instantly
when p-server wakes up,
instead of the worst-case scenario "push-mailqueue" :23h 59m 59s delayed.

Best regards,
Marius

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Re: sendind email to an intermittently connected host [ In reply to ]
On Tue, Jan 18, 2022 at 3:58 PM Cyborg via Exim-users <exim-users@exim.org>
wrote:

> Am 18.01.22 um 12:02 schrieb Odhiambo Washington via Exim-users:
> > Hi Leonardo,
> >
> > If I were you, I'd approach the problem a different way. I remember doing
> > something like that with intermittently connected hosts.
> > I would instead just queue the messages and let p.example.com to request
> > for their delivery when its connection comes up.
> >
> > Please refer to this link for the details:
> > https://plonk.de/sw/odmr/index.php
> >
>
> You mean someting like a message box, that gets pulled from p-server
> when it gets online.


Exactly. Messages would be saved in bsmtp files and would be pulled by
p-server when it gets online.


> Some office mailserver do this, so there is matching configs and software
> available.
>

I used this method during the days when broadband wasn't quite
well-developed. Worked flawlessly.


> IMHO, sounds like the better option, because messing it's save in the
> mailbox, can be accessed from anywhere else and is available instantly
> when p-server wakes up, instead of the worst-case scenario
> "push-mailqueue" :23h 59m 59s delayed.
>

That's what I thought. However the OP would rather mess up with the retry
times :-)



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Best regards,
Odhiambo WASHINGTON,
Nairobi,KE
+254 7 3200 0004/+254 7 2274 3223
"Oh, the cruft.", egrep -v '^$|^.*#' :-)
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Re: sendind email to an intermittently connected host [ In reply to ]
On 18/01/2022 15:24, Odhiambo Washington via Exim-users wrote:
> he OP would rather mess up with the retry
> times

To be fair, that's the quickest way to ensure that Exim doesn't
freeze or bounce a message waiting in spool, which is needed
whatever the eventual delivery method is.

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Jeremy

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Re: sendind email to an intermittently connected host [ In reply to ]
On 2022-01-18, Leonardo Boselli via Exim-users <exim-users@exim.org> wrote:
> On Tue, 18 Jan 2022, Odhiambo Washington wrote:
>> I still believe that it's better to solve the problem from the source -
>> where the connectivity is almost unpredictable.
>
> log time unconnections are predictable, since does not occour by a
> failure, but intentionally, and system manager for both systems is the
> same. so when system return active the unqueuing can be triggered
> manually.
> And the problem is not for 5 minutes (that BTW is NOT enough realtime
> for one of the the needs) but when it is off/inactive/refusing for up to 3
> months, when the other system must queue without giving even the slightest
> warning.

exim can be configured how long to retry for and when to warn,
you can set it to 6 months if you want (well, you might have to say
183 days I don't think exim understands months)

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Re: sendind email to an intermittently connected host [ In reply to ]
On 1/19/22 08:57, Jasen Betts via Exim-users wrote:
> exim can be configured how long to retry for and when to warn,
> you can set it to 6 months if you want (well, you might have to say
> 183 days I don't think exim understands months)

Maximum seems to bee weeks:
s seconds
m minutes
h hours
d days
w weeks

Olaf
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Re: sendind email to an intermittently connected host [ In reply to ]
Mandi! Leonardo Boselli via Exim-users
In chel di` si favelave...

> What is easier way ?

Not 'easier', but... consider also some 'offline' transport system, like
UUCP.

On online host you queue email to UUCP, and intermittent host simply fetch
them when needed.

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