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200160Long time sending

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  • Jan Steinman
    Jul 1, 2006
      I know the drill, but before you start in with "show us the logs," consider that this problem is generating some 60MB of logs EACH DAY!

      I have changed locations and servers, going from a 350MHz G4 to a 2.5GHz quad G5, from 128kB IDSL to 4MB ADSL. (Both are supposed to be "commercial quality" connections, which in this case, simply means more expensive.) "Should be a lot faster," I thought.

      But sending from other machines on our network takes increasingly long times after starting the server. It has been three days since a restart, and it now takes about 20 seconds pause between hitting "send" and having the message leave the queue.

      There are over a hundred process entries like the following:
        postfix   2272   0.0 -0.0    27524    924  ??  S     4:33PM   0:00.03 smtpd -n smtp -t inet -u

      Checking logs, I am getting 10-20 rejects PER MINUTE! All of them appear to be legit rejects -- generally "User unknown in local recipient table". Although I have had one or two people tell me their legit email was bounced, we seem to be getting most (if not all) our legit email. I suspect the bounces are a result of Inadvertent Denial of Service from the heavy reject traffic.

      I am using "virtual_maps = hash:/etc/postfix/virtual". I have not set "relay_recipient_maps" nor "local_recipient_maps".

      I suspect that spammers are hitting me particularly hard because my network segment is known to be a residential high-speed subnet, whereas I rarely got more than a few per minute on my old, slow IDSL subnet -- they didn't bother.

      I am not doing any particular postfix spam prevention -- but neither was I before, on my IDSL connection.

      I suspect that the volume of spam rejected is what is causing the extremely slow legit relaying through my SMTP server from machines on my subnet. I have also enabled a few discrete addresses for relaying (via "mynetworks") for places where I frequent wireless networks.

      So I'm thinking of doing one or more of the following:

      1) aggressive firewalling to block it BEFORE postfix sees it: CONS: a lot of work, may block legit email, the spammers keep moving

      2) start a second postfix instance on a different port, and use it exclusively for outbound email: CONS: does nothing to reduce the huge load on my incoming service

      3) switch IAPs: CONS: a pain in the neck, and they're all resellers, anyway, so I'd probably still end up on the same residential ADSL subnet

      4) Tweak main.cf somehow that I don't understand: CONS: if postfix still has to look at it, it still slows it down, no?

      5) Throttle the number of smtpd process instances: CONS: may increase Inadvertent Denial of Service to legit SMTP traffic.

      6) Your Idea Here! Feel free to steer me to a URL, FAQ, or book.

      Thanks in advance for any advice offered!

      :::: Jan Steinman, Communication Steward, EcoReality: http://www.EcoReality.org ::::
      :::: 160 Sharp Road, Salt Spring Island, BC V8K 2P6, Canada, 250.537.2024 ::::


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