Controlling concurrency for just outbound mail

[Alex]

Hi,

I'm not sure the subject of my email accurately reflects what I'm trying to do, but I'd like to limit the number of messages that are sent in a particular interval. We have a fedora20 server with postfix-2.10.3 that is a mail relay and mail store for a few hundred users.  On occasion, a message will be sent from the server in another department to a hundred users on this server, containing a very large attachment. A large number of users use a .forward to forward their mail off to another system such as Gmail or Yahoo, which sometimes results in messages such as this:

Aug 10 17:34:39 email01 postfix/smtp[14212]: EBC0E4158E: host a7fdb7788f74cdafaf2e1e53f35d9d.pamx1.hotmail.com[65.54.188.78] said: 421 PR(ct1) (BAY004-PAMC1F5) Unfortunately, some messages from 66.XXX.YYY.100 weren't sent. Please try again. We have limits for how many messages can be sent per hour and per day. You can also refer to http://mail.live.com/mail/troubleshooting.aspx#errors. (in reply to MAIL FROM command)

It also has the effect of consuming all the available bandwidth on our circuit when 50 outbound connections at once are made to that remote system.

Outbound mail need not be delivered immediately. I'd like to somehow control the flow of outbound mail to avoid saturating the 10mbs link we have to the Internet, as well as possibly affecting our reputation with Gmail and Yahoo.

I experimented with (local|default)_destination_concurrency_limit some time ago, and users were complaining about "connection refused" errors, if I recall correctly, because I think it affected inbound SMTP connections as well.

I hoped someone could help me get started. Is it possible to limit the number of outbound connections in total, or only to specific destinations?

Thanks,
Alex

[li...@rhsoft.net]

Am 07.09.2014 um 02:03 schrieb Alex:
> Outbound mail need not be delivered immediately. I'd like to somehow control the flow of outbound mail to avoid
> saturating the 10mbs link we have to the Internet, as well as possibly affecting our reputation with Gmail and Yahoo.
>
> I experimented with (local|default)_destination_concurrency_limit some time ago, and users were complaining about
> "connection refused" errors, if I recall correctly, because I think it affected inbound SMTP connections as well

things like below staring with smtp_ can't affect inbound by definition

smtp_destination_recipient_limit = 15
smtp_initial_destination_concurrency = 2
smtp_destination_concurrency_limit = 2
smtp_destination_concurrency_failed_cohort_limit = 10
smtp_destination_rate_delay = 1
smtp_connection_cache_time_limit = 3

[Wietse Venema]

Postfix has no bit-rate controls. If you want to reduce Postfix
network bitrates, then use traffic shaping in your TCP/IP stack.

If you want to limit the mail volume to a Yahoo etc., use Postfix
built-in concurrency limits. Configure dedicated SMTP clients in
master.cf for Yahoo etc. and use reduced concurrency limit etc.
values.

/etc/postfix/master.cf:
yahoo unix - - n - - smtp

/etc/postfix/main.cf:
yahoo_destination_concurrency_limit = 1
yahoo_destination_rate_delay = 1
yahoo_destination_recipient_limit = whatever

Wietse