Outlook.com Max Connections

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Outlook.com Max Connections

Greg Sims
Here are the stats from this morning:

  * email arrival rate: 1,000/minute
  * outlook.com email sent: 7,113
  * MaxConnections: 17

MaxConnections increases with the email arrival rate.  It is consistent day to day at a given email arrival rate.  We are currently running four outlook transports on different ip addresses with connection caching disabled.  Each of these transports are running two processes.

Three possibilities come to mind:

  (1) continue to ignore the MaxConnection Messages/Deferrals
  (2) reduce the number of processes per transport to 1
  (3) reduce the number of outlook transports to 2

I do not believe (3) will help as I believe outlook servers are watching connections on a per ip basis from looking at the maillogs.  I'm leaning towards (2) but I am not sure of the ramifications of running one process per transport.  Perhaps there are other solutions I have not considered.

Thanks, Greg
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Re: Outlook.com Max Connections

Wietse Venema
Greg Sims:

> Here are the stats from this morning:
>
>   * email arrival rate: 1,000/minute
>   * outlook.com email sent: 7,113
>   * MaxConnections: 17
>
> MaxConnections increases with the email arrival rate.  It is consistent day
> to day at a given email arrival rate.  We are currently running four
> outlook transports on different ip addresses with connection caching
> disabled.  Each of these transports are running two processes.
>
> Three possibilities come to mind:
>
>   (1) continue to ignore the MaxConnection Messages/Deferrals
>   (2) reduce the number of processes per transport to 1
>   (3) reduce the number of outlook transports to 2
>
> I do not believe (3) will help as I believe outlook servers are watching
> connections on a per ip basis from looking at the maillogs.  I'm leaning
> towards (2) but I am not sure of the ramifications of running one process
> per transport.  Perhaps there are other solutions I have not considered.

17 deferrals out of 7,113 deliveries is not bad.

        Wietse
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Re: Outlook.com Max Connections

Viktor Dukhovni
In reply to this post by Greg Sims
On Mon, Aug 31, 2020 at 09:08:02AM -0700, Greg Sims wrote:

> Here are the stats from this morning:
>
>   * email arrival rate: 1,000/minute
>   * outlook.com email sent: 7,113
>   * MaxConnections: 17

Theseare perhaps a result of some domains hosted by outlook.com, but not
included in your list of domains to route to the dedicated transports.
You might consider using one of the 4 four transports with the (long
ago up-thread) suggestion to:

    main.cf:
        ...
        smtpd_recipient_restrictions =
            check_recipient_mx_access <sometable>

    <sometable>
        # insert all relevant MX host domains here
        .outlook.com    FILTER transport4
        .hotmail.com    FILTER transport4
        ...

and using the other 3 round-robin for the *known* domains, but *raising*
the concurrency limits from 2 to 5 or so, because you now are no longer
competing on the same IPs with the messages that sneak by the static
tables.

--
    Viktor.
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Re: Outlook.com Max Connections

@lbutlr
In reply to this post by Greg Sims
On 31 Aug 2020, at 10:08, Greg Sims <[hidden email]> wrote:
>   (1) continue to ignore the MaxConnection Messages/Deferrals
>   (2) reduce the number of processes per transport to 1
>   (3) reduce the number of outlook transports to 2

4) add a footer to mails going to outlook along the lines of :"messages to outlook users may be delayed because outlook.com is a garbage service."

I kid.

Sort of.




--
'Listen,' said Rincewind. 'It's all over, do you see? You can't put
        the spells back in the book, you can't unsay what's been said,
        you can't-' 'You can try!' --The Light Fantastic

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Re: Outlook.com Max Connections

Greg Sims
In reply to this post by Viktor Dukhovni
> > Here are the stats from this morning:
> >
> >   * email arrival rate: 1,000/minute
> >   * outlook.com email sent: 7,113
> >   * MaxConnections: 17

> These are perhaps a result of some domains hosted by outlook.com, but not
> included in your list of domains to route to the dedicated transports.

This is an interesting thought Viktor -- thank you.  I checked the
logs and saw only one message that used an outlook.com relay that did
not use one of the four outlook transports.  This outlook email
address is a recent subscription to our devotion email.  You would
likely agree that one outlook email not using the outlook dedicated
transports is not the cause of 17 MaxConnections.

The "static" transport table is generated as part of our log analysis
each morning after we deliver the email for the day.  Perhaps we can
call this "semi-dynamic" transport table.  It is a good day for us to
20 additional subscriptions net (subscribes less unsubscribes) across
all email address domains.  I do not believe the transport.regexp and
the devotion emails actually sent will ever get far out of sync.  I
can change the crontab to rebuild the transport.regexp in the early
morning just before the Spanish and English runs begin -- this would
close the gap even further.

One key problem we are facing is a high density of outlook.com emails
from Spanish speaking subscribers.  Here are the morning run stats for
our devotion emails in Spanish:

                                         Email     Ave      Max      conn
      Relay                           Sent    Delay    Delay     use=
      outlook.com                  4,747        4      391         0
      google.com                   4,517        1       24      529
      yahoodns.net                   675        1        3           0
         < 100 Email Sent skipped (some exceptions); all in Total
      Total                            10,123      2.3      391      529

    Maillog Summary:
      Google       -- UserOverquota_Deferred: 44
      Outlook      -- Connection: 16, MaxConnections: 16,
MaxConnections_Deferred: 5

The Spanish devotions sent 4,747 emails to Outlook out of 10,123 Total
-- a density of 47%.  This Spanish group got 16 of the 17
MaxConnections.

The English devotions sent 2,366 to Outlook out of 19,620 Total -- a
density of only 12%  The English group saw the remaining 1
MaxConnections.

Microsoft must be doing a good job of marketing to Spanish speaking regions.

Here is some additional information that is hope is *Not* related.  I
received four emails this morning from Spanish speaking people that
did not receive a devotion -- I directed them to look in their Spam
Folder.  I also saw that Microsoft SNDS status went from "yellow" to
"red" for our IP addresses this morning.

Thanks, Greg
www.RayStedman.org


Blessings, Greg
www.RayStedman.org


On Mon, Aug 31, 2020 at 1:24 PM Viktor Dukhovni
<[hidden email]> wrote:

>
> On Mon, Aug 31, 2020 at 09:08:02AM -0700, Greg Sims wrote:
>
> > Here are the stats from this morning:
> >
> >   * email arrival rate: 1,000/minute
> >   * outlook.com email sent: 7,113
> >   * MaxConnections: 17
>
> Theseare perhaps a result of some domains hosted by outlook.com, but not
> included in your list of domains to route to the dedicated transports.
> You might consider using one of the 4 four transports with the (long
> ago up-thread) suggestion to:
>
>     main.cf:
>         ...
>         smtpd_recipient_restrictions =
>             check_recipient_mx_access <sometable>
>
>     <sometable>
>         # insert all relevant MX host domains here
>         .outlook.com    FILTER transport4
>         .hotmail.com    FILTER transport4
>         ...
>
> and using the other 3 round-robin for the *known* domains, but *raising*
> the concurrency limits from 2 to 5 or so, because you now are no longer
> competing on the same IPs with the messages that sneak by the static
> tables.
>
> --
>     Viktor.
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Re: Outlook.com Max Connections

Tom Sommer
In reply to this post by @lbutlr

On 2020-09-01 00:28, @lbutlr wrote:

> On 31 Aug 2020, at 10:08, Greg Sims <[hidden email]> wrote:
>>   (1) continue to ignore the MaxConnection Messages/Deferrals
>>   (2) reduce the number of processes per transport to 1
>>   (3) reduce the number of outlook transports to 2
>
> 4) add a footer to mails going to outlook along the lines of
> :"messages to outlook users may be delayed because outlook.com is a
> garbage service."
>
> I kid.
>
> Sort of.

Truth