On Tue, Jan 08, 2013 at 10:47:08AM -0200, Rafael Azevedo - IAGENTE wrote:
> I've added this into my main.cf:
>
> slow_destination_concurrency_failed_cohort_limit = 5
This is fine, since you set the concurrency limit to 1, it is
intended to avoid shutting down deliveries after a single connection
failure. As Wietse points out this does not stop deliveries when
individual recipients are rejected, that is not evidence of the
site being down.
> Question: how can I stop postfix from trying to deliver emails
> after few failures?
It is not possible to aumatically throttle deliveries based on 4XX
replies to RCPT TO. This is not a useful signal that Postfix is
sending "too fast", nor is there any good way to dynamically
determine the correct rate.
Sites that impose indiscriminate (assuming you're sending legitimate
email, not spam) rate controls are breaking the email infrastructure.
Sadly, the work-around is to snowshoe---deploy more servers to split the
load over a larger number of IP addresses.
> I mean, if it is trying to deliver to xyz.com and it fails 5
> times, should postfix keep trying to deliver or is there any way
> that we can stop delivering for some time?
Only if xyz.com is down, not if it is merely tempfailing RCPT TO.
> This is the error I get:
> said: 450 4.7.1 You've exceeded your sending limit to this domain.
> (in reply to end of DATA command))
Since presumably at this point your connection rate is not high
(connections are being re-used), it seems that they're imposing
a message rate cap as well as a connection rate cap.
Send them less email.
> I'm really trying to slow down the delivery speed in order to
> respect the destination's policies. I just can't figure out how to
> fix this issue.
>
> We send about 50k emails/day to 20k domains hosted on this provider
> that are being blocked.
The output rate cannot on average fall below the input rate. The
input rate is approximately 1/sec (there are 86400 seconds in a
day). Thus the slowest you can send is with a rate delay" of 1s.
If that's not slow enough, you're out of luck, and have to buy
more servers (possibly deploying them on separate networks).
The suggestion to turn off rate delays was based on an assumption
that they told you to avoid connecting too often and wanted all
the mail over a single connection (you wanted connection re-use),
but connection re-use works best when there is no rate delay.
A rate delay of 1s is still compatible with connection re-use,
and is the largest you can specify and still send more than
43.2k messages a day.
It may be simplest to outsource your traffic to an existing large
bulk email operator.
--
Viktor.
