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Re: 421 too many messages in this connection

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  • Noel Jones
    ... Postfix can reuse a connection if there is a lot of mail for a single destination. The destination might disconnect at some point, after which postfix is
    Message 1 of 3 , Sep 1 2:42 PM
      On 9/1/2013 3:20 PM, Roman Gelfand wrote:
      > I am not sure I understand this. Isn't every message a separate connection?
      >
      > If what it means to say is I have exceeded a quota for sending out
      > emails per time period, what is there to do about it?
      >
      > Thanks in advance
      >

      Postfix can reuse a connection if there is a lot of mail for a
      single destination. The destination might disconnect at some point,
      after which postfix is free to try again.

      Generally you can ignore this and it will sort itself out.

      If it doesn't sort itself out in a reasonable amount of time, you
      can configure delivery delays for that destination.

      Some reading, but a warning that ill-considered changes can make
      things worse:
      http://www.postfix.org/QSHAPE_README.html
      http://www.postfix.org/TUNING_README.html



      -- Noel Jones
    • AFCommerce LLC
      Also take a look at the following settings in the postconf docs: default_destination_recipient_limit default_destination_concurrency_limit
      Message 2 of 3 , Sep 1 6:37 PM
        Also take a look at the following settings in the postconf docs:  

        default_destination_recipient_limit

        default_destination_concurrency_limit

        initial_destination_concurrency

        queue_run_delay

        Their importance to you (in my opinion) are listed in order, the first setting I listed is what is most likely affecting things the most. The default settings though should be perfect for most people. 
         - to see your current settings type on the command line: 
        postconf default_destination_recipient_limit default_destination_concurrency_limit initial_destination_concurrency queue_run_delay

        Postfix has some nice logic for reusing connections, so that you don't have to worry or understand how delivery works, but lets say you had 100 emails to hotmail in (or around) the same time, an mta can make 100 connections to hotmail at the same time (concurrency) with one message each, or could make 1 connection and send all 100 in one connection, or a mix, for example making 10 connections with 10 emails sent in each. There's no limit to what you tell postfix to send, or I should say "attempt to send", however what the receiving ISP (like hotmail) will accept from you varies greatly depending on your mailing domain/ip's reputation, so there's no global numbers we can tell you that will work for everyone. It also varies per ISP, like gmail may tolerate less connections/recipients than hotmail or vice versa.

        Too many messages error = that ISP wants less per connection, and the opposite error, "too many connections" means you should send more each connection, but if you're sending a lot of mail chances are they just won't want to see as much from you in a short time frame and you will just have to slow down the total messages sent, so I'd say *slightly* lower your default_destination_recipient_limit and see if that helps and if you start getting too many connection errors, then you know its just too much mail to send that fast. Also, if you are hitting any kind of sending problem like that, you probably have another program injecting messages to postfix, like a newsletter program etc. If that's the case, slow that script down and leave postfix alone, its nice that postfix figures this stuff out for you, but when things go wrong its the sender's fault not the mta. 

        IP reputation is beyond the scope of this discussion so if you want more info on it search for yahoo's postmaster doc's which explain it very well, hotmail's docs are decent too. 

        Paul



        On Sun, Sep 1, 2013 at 5:42 PM, Noel Jones <njones@...> wrote:
        On 9/1/2013 3:20 PM, Roman Gelfand wrote:
        > I am not sure I understand this.  Isn't every message a separate connection?
        >
        > If what it means to say is I have exceeded a quota for sending out
        > emails per time period, what is there to do about it?
        >
        > Thanks in advance
        >

        Postfix can reuse a connection if there is a lot of mail for a
        single destination.  The destination might disconnect at some point,
        after which postfix is free to try again.

        Generally you can ignore this and it will sort itself out.

        If it doesn't sort itself out in a reasonable amount of time, you
        can configure delivery delays for that destination.

        Some reading, but a warning that ill-considered changes can make
        things worse:
        http://www.postfix.org/QSHAPE_README.html
        http://www.postfix.org/TUNING_README.html



          -- Noel Jones

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