On 18/11/2025 16:19, David Higton wrote:

In message <10fhnjv$1gvnc$5@dont-email.me>
The Natural Philosopher <tnp@invalid.invalid> wrote:

As part of my enhancements to the home controller, I want to send email
warnings of low heating oil level.

Have a look at Pushover to see if it would be an alternative way to
meet your needs. I use it to alert myself of problems in my heating
system.

David

my system is tailored to my needs. It works perfectly. I just need to
extend it a little. Nothing I can buy suited, so I rolled my own with
Pis and Picos.

Its actually one of the best bits of hardware and software I have ever done.

BUT it seems that the Pi will retry the queued mail and get it right on
the second attempt, so I may just leave it...

--
?A leader is best When people barely know he exists. Of a good leader,
who talks little,When his work is done, his aim fulfilled,They will say,
?We did this ourselves.?

? Lao Tzu, Tao Te Ching


--- PyGate Linux v1.5
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

On 18/11/2025 21:08, Computer Nerd Kev wrote:

The Natural Philosopher <tnp@invalid.invalid> wrote:

Seriously,m its not the server, its the DNS.

It (the PI) cant even *find* the SMTP server
Nov 18 10:46:56 heating-controller postfix/pickup[8654]: CC05B1F270:
uid=0 from=<oil-monitor@heating-controller>
Nov 18 10:46:56 heating-controller postfix/cleanup[10455]: CC05B1F270:
message-id=<20251118104656.CC05B1F270@heating-controller>
Nov 18 10:46:56 heating-controller postfix/qmgr[1295]: CC05B1F270:
from=<oil-monitor@heating-controller>, size=387, nrcpt=1 (queue active)
Nov 18 10:46:57 heating-controller postfix/smtp[10457]: CC05B1F270:
to=<superroot@templar.co.uk>, relay=none, delay=0.38,
delays=0.19/0.14/0.04/0, dsn=4.4.3, status=deferred (Host or domain name
not found. Name service error for name=vps.templar.co.uk type=MX: Host
not found, try again)

If it's the only network activity the thing does regularly, maybe
the WiFi interface has gone into some sort of sleep mode and the DNS
resolver isn't waiting for it to wake up. If you leave ping running
(eg. "nohup ping -s 1 vps.templar.co.uk &") to keep the interface
active, maybe it will work the first time?

I was logged in over ssh at the time, so that hound don't hunt :-(

Or if it doesn't change, you could set the IP address for
vps.templar.co.uk in /etc/hosts.

That could be a workaround. Good idea


--
All political activity makes complete sense once the proposition that
all government is basically a self-legalising protection racket, is
fully understood.



--- PyGate Linux v1.5
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

The Natural Philosopher <tnp@invalid.invalid> wrote:

Seriously,m its not the server, its the DNS.

It (the PI) cant even *find* the SMTP server
Nov 18 10:46:56 heating-controller postfix/pickup[8654]: CC05B1F270:
uid=0 from=<oil-monitor@heating-controller>
Nov 18 10:46:56 heating-controller postfix/cleanup[10455]: CC05B1F270: message-id=<20251118104656.CC05B1F270@heating-controller>
Nov 18 10:46:56 heating-controller postfix/qmgr[1295]: CC05B1F270: from=<oil-monitor@heating-controller>, size=387, nrcpt=1 (queue active)
Nov 18 10:46:57 heating-controller postfix/smtp[10457]: CC05B1F270: to=<superroot@templar.co.uk>, relay=none, delay=0.38, delays=0.19/0.14/0.04/0, dsn=4.4.3, status=deferred (Host or domain name
not found. Name service error for name=vps.templar.co.uk type=MX: Host
not found, try again)

If it's the only network activity the thing does regularly, maybe
the WiFi interface has gone into some sort of sleep mode and the DNS
resolver isn't waiting for it to wake up. If you leave ping running
(eg. "nohup ping -s 1 vps.templar.co.uk &") to keep the interface
active, maybe it will work the first time?

Or if it doesn't change, you could set the IP address for
vps.templar.co.uk in /etc/hosts.

--
__ __
#_ < |\| |< _#

--- PyGate Linux v1.5
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

In message <10fhnjv$1gvnc$5@dont-email.me>
The Natural Philosopher <tnp@invalid.invalid> wrote:

As part of my enhancements to the home controller, I want to send email warnings of low heating oil level.

Have a look at Pushover to see if it would be an alternative way to
meet your needs. I use it to alert myself of problems in my heating
system.

David

--- PyGate Linux v1.5
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

The Natural Philosopher <tnp@invalid.invalid> wrote:

As part of my enhancements to the home controller, I want to send email warnings of low heating oil level.

So I removed exim which was too much like hard work, installed PostFix
and all is well...,except it isn't.

If I send a mail out of the blue after a a few hours delay, the mail immediately *always* gets stuck in the queue with a message about being unable to determine the IP address of the SMTP relay.

If I send another message everything Just Works, and indeed the h mail
queue gets flushed eventually as well with a successful delivery.

'Greylisting'? SMTP servers often delay mail from unrecognised senders as a spam block - spammers tend not come back when told to try again later.

Also the message needs to be correct to match SFP/DKIM/DMARC rules,
otherwise it may get delayed or discarded. It may also be delayed/discarded due to sending from a 'consumer' IP.

Perhaps by the time the second message arrives the spamfilter has decided you're ok and to let the message straight through.

I would not be doing direct SMTP in this day and age - send using an SMTP account (with username/password) at the company who runs the SMTP server for the sender's mail domain.

If the SMTP relay is indeed your domain's mail server, perhaps the first
time DNS lookup is too slow?

Theo

--- PyGate Linux v1.5
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

As part of my enhancements to the home controller, I want to send email warnings of low heating oil level.

So I removed exim which was too much like hard work, installed PostFix
and all is well...,except it isn't.

If I send a mail out of the blue after a a few hours delay, the mail immediately *always* gets stuck in the queue with a message about being
unable to determine the IP address of the SMTP relay.

If I send another message everything Just Works, and indeed the h mail
queue gets flushed eventually as well with a successful delivery.

I have looked on line but not found this exact behaviour mentioned
anywhere..

I am not sure what is running DNS on that Zero W right now. But its
clo9ck is up to date with the internet...,




--
Future generations will wonder in bemused amazement that the early twenty-first century?s developed world went into hysterical panic over a globally average temperature increase of a few tenths of a degree, and,
on the basis of gross exaggerations of highly uncertain computer
projections combined into implausible chains of inference, proceeded to contemplate a rollback of the industrial age.

Richard Lindzen

--- PyGate Linux v1.5
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

On 18/11/2025 14:37, Theo wrote:

The Natural Philosopher <tnp@invalid.invalid> wrote:

As part of my enhancements to the home controller, I want to send email
warnings of low heating oil level.

So I removed exim which was too much like hard work, installed PostFix
and all is well...,except it isn't.

If I send a mail out of the blue after a a few hours delay, the mail
immediately *always* gets stuck in the queue with a message about being
unable to determine the IP address of the SMTP relay.

If I send another message everything Just Works, and indeed the h mail
queue gets flushed eventually as well with a successful delivery.

'Greylisting'? SMTP servers often delay mail from unrecognised senders as a spam block - spammers tend not come back when told to try again later.

Its my smtp server. Sorry I didn't make that clear. No greylisting that
I am aware of

Also the message needs to be correct to match SFP/DKIM/DMARC rules,
otherwise it may get delayed or discarded. It may also be delayed/discarded due to sending from a 'consumer' IP.

Again, there is no issue as its set to accept any mail from anywhere
that is addressed to my home network.

Perhaps by the time the second message arrives the spamfilter has decided you're ok and to let the message straight through.

Seriously,m its not the server, its the DNS.

It (the PI) cant even *find* the SMTP server
Nov 18 10:46:56 heating-controller postfix/pickup[8654]: CC05B1F270:
uid=0 from=<oil-monitor@heating-controller>
Nov 18 10:46:56 heating-controller postfix/cleanup[10455]: CC05B1F270: message-id=<20251118104656.CC05B1F270@heating-controller>
Nov 18 10:46:56 heating-controller postfix/qmgr[1295]: CC05B1F270: from=<oil-monitor@heating-controller>, size=387, nrcpt=1 (queue active)
Nov 18 10:46:57 heating-controller postfix/smtp[10457]: CC05B1F270: to=<superroot@templar.co.uk>, relay=none, delay=0.38,
delays=0.19/0.14/0.04/0, dsn=4.4.3, status=deferred (Host or domain name
not found. Name service error for name=vps.templar.co.uk type=MX: Host
not found, try again)
Nov 18 10:56:42 heating-controller postfix/qmgr[1295]: CC05B1F270: from=<oil-monitor@heating-controller>, size=387, nrcpt=1 (queue active)
Nov 18 10:56:43 heating-controller postfix/smtp[10697]: CC05B1F270: to=<superroot@templar.co.uk>,
relay=vps.templar.co.uk[185.113.128.151]:25, delay=587, delays=586/0.22/0.64/0.08, dsn=2.0.0, status=sent (250 OK
id=1vLJO7-0000r9-GS)
Nov 18 10:56:43 heating-controller postfix/qmgr[1295]: CC05B1F270: removed

I would not be doing direct SMTP in this day and age - send using an SMTP account (with username/password) at the company who runs the SMTP server for the sender's mail domain.

Sigh. I do for mail outward bound, but this is actually inward boiund.

If the SMTP relay is indeed your domain's mail server, perhaps the first
time DNS lookup is too slow?

Its something like that.

Let me say that all other boxes inside the network that are equipped for
mail work fine

Theo

--
For every complex problem there is an answer that is clear, simple, and
wrong.

H.L.Mencken


--- PyGate Linux v1.5
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

On Tue, 18 Nov 2025 15:27:01 +0000, The Natural Philosopher wrote:

Seriously,m its not the server, its the DNS.

What are you running as your DNS server?

Nov 18 10:46:57 heating-controller postfix/smtp[10457]: CC05B1F270: to=<superroot@templar.co.uk>, relay=none, delay=0.38, delays=0.19/0.14/0.04/0, dsn=4.4.3, status=deferred (Host or domain
name not found. Name service error for name=vps.templar.co.uk
type=MX: Host not found, try again)

You could try doing a lookup (using host or dig) to your DNS server
from the Raspberry pi at the same time as the MTA is reporting
problems, and see if your manual query reports the same problem.

Does your /etc/resolv.conf contain the right info? Is it a symlink to
somewhere else?

--- PyGate Linux v1.5
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

On 18/11/2025 12:08, The Natural Philosopher wrote:

As part of my enhancements to the home controller, I want to send email warnings of low heating oil level.

This sounds rather like something I have been planning to do. AAMOI how
are you measuring the oil level?

--
Cheers,
Daniel.

--- PyGate Linux v1.5
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)