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split up mail

richard lucassen
Hello list,

For a few reasons I use an outgoing postfix as smarthost. The source
mailserver is an exchange. Before the postfix server was in use,
sending mail to a bunch of recipients at a domain which is hosted by
outlook.com was no problem. When the mail passes through postfix, mail
to many recipients at a domain hosted by outlook.com is delayed and this
is the message I see in the queue:

-Queue ID-  --Size-- ----Arrival Time---- -Sender/Recipient-------
EA57C5F8D9     7094 Mon May 15 14:41:09  [hidden email]
(host 358619467.mail.outlook.com[213.199.154.106] said: 452 4.5.3 Too
many recipients (AS780090)
[AM5EUR03FT055.eop-EUR03.prod.protection.outlook.com] (in reply to RCPT
TO command))

Searching a bit I found this setting:

smtp_destination_recipient_limit

This defaults to 50. Is this the right parameter to adjust?

R.

--
richard lucassen
http://contact.xaq.nl/
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Re: split up mail

Wietse Venema
richard lucassen:

> Hello list,
>
> For a few reasons I use an outgoing postfix as smarthost. The source
> mailserver is an exchange. Before the postfix server was in use,
> sending mail to a bunch of recipients at a domain which is hosted by
> outlook.com was no problem. When the mail passes through postfix, mail
> to many recipients at a domain hosted by outlook.com is delayed and this
> is the message I see in the queue:
>
> -Queue ID-  --Size-- ----Arrival Time---- -Sender/Recipient-------
> EA57C5F8D9     7094 Mon May 15 14:41:09  [hidden email]
> (host 358619467.mail.outlook.com[213.199.154.106] said: 452 4.5.3 Too
> many recipients (AS780090)
> [AM5EUR03FT055.eop-EUR03.prod.protection.outlook.com] (in reply to RCPT
> TO command))
>
> Searching a bit I found this setting:
>
> smtp_destination_recipient_limit
>
> This defaults to 50. Is this the right parameter to adjust?

Maybe. In the fight against spam, mail server operators are not
exactly famous for providing accurate error messages.

The SMTP standard says the server should accept 100 or more recipients
in the same MAIL FROM transaction, and it specifies no limit on the
number of MAIL FROM transactions in the same SMTP session. Mail
operators on the other hand may do all kinds of arbitrary things.

Working around this may involve a combination of Postfix rate_delay
and other settings. Donate your eyeballs to your preferred search
engine to find out what other people do. My domain is too small
to provide meaningful experience in this respect.

        Wietse
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Re: split up mail

Marco-3

Hello.

I have been supporting for years no-profit organizations, that have been sending a number of mails to 10000 and more recipients at the same time.

After similar initial problems the solution never giving any major issue was

default_destination_concurrency_limit = 1
default_destination_recipient_limit = 25

Of course this slows down the delivery, however it is not a big problem unless all the recipients are handled by a restricted number of MX (and this is not usual)

I'm now running less intensive mail servers, so maybe some tuning is need in this phase.

Marco
Il 19. 05. 17 13:39, Wietse Venema ha scritto:
richard lucassen:
Hello list,

For a few reasons I use an outgoing postfix as smarthost. The source
mailserver is an exchange. Before the postfix server was in use,
sending mail to a bunch of recipients at a domain which is hosted by
outlook.com was no problem. When the mail passes through postfix, mail
to many recipients at a domain hosted by outlook.com is delayed and this
is the message I see in the queue:

-Queue ID-  --Size-- ----Arrival Time---- -Sender/Recipient-------
EA57C5F8D9     7094 Mon May 15 14:41:09  [hidden email]
(host 358619467.mail.outlook.com[213.199.154.106] said: 452 4.5.3 Too
many recipients (AS780090)
[AM5EUR03FT055.eop-EUR03.prod.protection.outlook.com] (in reply to RCPT
TO command))

Searching a bit I found this setting:

smtp_destination_recipient_limit

This defaults to 50. Is this the right parameter to adjust?
Maybe. In the fight against spam, mail server operators are not
exactly famous for providing accurate error messages.

The SMTP standard says the server should accept 100 or more recipients
in the same MAIL FROM transaction, and it specifies no limit on the
number of MAIL FROM transactions in the same SMTP session. Mail
operators on the other hand may do all kinds of arbitrary things.

Working around this may involve a combination of Postfix rate_delay
and other settings. Donate your eyeballs to your preferred search
engine to find out what other people do. My domain is too small
to provide meaningful experience in this respect.

	Wietse

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Re: split up mail

richard lucassen
In reply to this post by Wietse Venema
On Fri, 19 May 2017 07:39:37 -0400 (EDT)
[hidden email] (Wietse Venema) wrote:

> > Searching a bit I found this setting:
> >
> > smtp_destination_recipient_limit
> >
> > This defaults to 50. Is this the right parameter to adjust?
>
> Maybe. In the fight against spam, mail server operators are not
> exactly famous for providing accurate error messages.

So if I understand the docs correctly, setting this parameter to e.g.
25 has the following result:

1 message sent to 100 rcpt's -> postfix -> 4 messages to 25 rcpt's

Note: 100 rcpt's at the same domain of course.

Right or wrong?

R.

--
richard lucassen
http://contact.xaq.nl/
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Re: split up mail

Marco-3


Il 19. 05. 17 15:27, richard lucassen ha scritto:

> On Fri, 19 May 2017 07:39:37 -0400 (EDT)
> [hidden email] (Wietse Venema) wrote:
>
>>> Searching a bit I found this setting:
>>>
>>> smtp_destination_recipient_limit
>>>
>>> This defaults to 50. Is this the right parameter to adjust?
>> Maybe. In the fight against spam, mail server operators are not
>> exactly famous for providing accurate error messages.
> So if I understand the docs correctly, setting this parameter to e.g.default_destination_concurrency_limit = 1
> 25 has the following result:
>
> 1 message sent to 100 rcpt's -> postfix -> 4 messages to 25 rcpt's
>
> Note: 100 rcpt's at the same domain of course.
>
> Right or wrong?
>
> R.
>
Correct, however 25 was a good number only if
default_destination_concurrency_limit is set to 1, as i.e. if you have 2
you can have 2*25 recipients delivered in parallel and some servers have
been not happy with this.

Marco



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Re: split up mail

richard lucassen
On Fri, 19 May 2017 15:52:05 +0200
marco <[hidden email]> wrote:

> > So if I understand the docs correctly, setting this parameter to
> > e.g.default_destination_concurrency_limit = 1 25 has the following
> > result:
> >
> > 1 message sent to 100 rcpt's -> postfix -> 4 messages to 25 rcpt's
> >
> > Note: 100 rcpt's at the same domain of course.
> >
> > Right or wrong?
>
> Correct, however 25 was a good number only if
> default_destination_concurrency_limit is set to 1, as i.e. if you
> have 2 you can have 2*25 recipients delivered in parallel and some
> servers have been not happy with this.

Ah, that might be the issue then, when I leave these parameters
set to their defaults, it would mean that the maximum Postfix will send
at once is 20 mails containing 50 recipients?

So, according to you I should add:

smtp_destination_concurrency_limit = 1

to main.cf.

R.

--
richard lucassen
http://contact.xaq.nl/
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Re: split up mail

Marco-3
My setup was

default_destination_concurrency_limit = 1
default_destination_recipient_limit = 25

I never had major problems with this, it was only a little bit slow with
gmail, yahoo and other big mail accounts providers, anyway never a real
issue.

This setup is probably not perfect if you have a lot of mail users, as
one single mail with a lot of recipients will slow-down the delivery
until all the "sub-deliveries" are handled for a specific server.

Marco

Il 19. 05. 17 16:02, richard lucassen ha scritto:

> On Fri, 19 May 2017 15:52:05 +0200
> marco <[hidden email]> wrote:
>
>>> So if I understand the docs correctly, setting this parameter to
>>> e.g.default_destination_concurrency_limit = 1 25 has the following
>>> result:
>>>
>>> 1 message sent to 100 rcpt's -> postfix -> 4 messages to 25 rcpt's
>>>
>>> Note: 100 rcpt's at the same domain of course.
>>>
>>> Right or wrong?
>> Correct, however 25 was a good number only if
>> default_destination_concurrency_limit is set to 1, as i.e. if you
>> have 2 you can have 2*25 recipients delivered in parallel and some
>> servers have been not happy with this.
> Ah, that might be the issue then, when I leave these parameters
> set to their defaults, it would mean that the maximum Postfix will send
> at once is 20 mails containing 50 recipients?
>
> So, according to you I should add:
>
> smtp_destination_concurrency_limit = 1
>
> to main.cf.
>
> R.
>

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Re: split up mail

Viktor Dukhovni
In reply to this post by richard lucassen

> On May 19, 2017, at 10:02 AM, richard lucassen <[hidden email]> wrote:
>
> Ah, that might be the issue then, when I leave these parameters
> set to their defaults, it would mean that the maximum Postfix will send
> at once is 20 mails containing 50 recipients?
>
> So, according to you I should add:
>
> smtp_destination_concurrency_limit = 1

That's too fragile, at least without further tuning.  With this,
when any connection fails the destination concurrency is reduced
to 0, and the destination is immediately throttled.

If you don't send much mail, and latency is acceptable, you could
start going from 20 down 10 or 5.  Anything much lower and you
need to start tuning the advanced feedback controls...

Try and get whitelisted by outlook.com, that's better than taking
evasive countermeasures.

--
        Viktor.

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Re: split up mail

richard lucassen
On Fri, 19 May 2017 10:53:56 -0400
Viktor Dukhovni <[hidden email]> wrote:

> > So, according to you I should add:
> >
> > smtp_destination_concurrency_limit = 1
>
> That's too fragile, at least without further tuning.  With this,
> when any connection fails the destination concurrency is reduced
> to 0, and the destination is immediately throttled.

ok

> If you don't send much mail, and latency is acceptable, you could
> start going from 20 down 10 or 5.  Anything much lower and you
> need to start tuning the advanced feedback controls...
>
> Try and get whitelisted by outlook.com, that's better than taking
> evasive countermeasures.

We tried but no way. Next monday we'll have another try. It seems that
it has to do with ip and domain reputation, there have been some
issues in the past. We'll find that out next week I hope.

R.

--
richard lucassen
http://contact.xaq.nl/
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