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Re: avoiding overload on port 587

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  • Stan Hoeppner
    ... My apologies for the mis-attribution Wietse. I agree not all virtual environments have clock problems serious enough to avoid deploying mail servers. I
    Message 1 of 54 , Nov 30, 2012
      On 11/30/2012 6:08 PM, Wietse Venema wrote:
      > Stan Hoeppner:
      >> That said, given the ongoing clock issues that all the guest/hypervisor
      >> combos have always experienced to some degree, and will forever
      >> experience no matter how good the mitigation hacks, it is my opinion,
      >> and Wietse's, and many others, that mail is not really a suitable
      >> application for most virtual environments. I'm sure you'll now write at
      >
      > Um, I have pointed out failures. I do not claim that all virtualization
      > environments fail to meet the requirements.
      >
      > Wietse


      My apologies for the mis-attribution Wietse. I agree not all virtual
      environments have clock problems serious enough to avoid deploying mail
      servers. I stated "most", which may likely be better described today as
      "many". It's still a problem with Linux on ESX though not as bad as it
      once was, and it's bad today with Linux on Linux. I would think with
      IBM's ingenuity and 30 some years of virtual machine experience that
      Linux on zSeries would have no clock drift at all, but I have no first
      hand experience with this platform, and I have no experience and pay no
      attention to what Oracle is doing with Solaris virtualization,
      "containers" I believe they call it.

      --
      Stan
    • /dev/rob0
      ... Or better yet: replace it with postscreen. ... To clarify, I meant that if those Outlook Expresses are not yet compromised by malware, they will be, soon.
      Message 54 of 54 , Dec 4, 2012
        On Tue, Dec 04, 2012 at 07:46:10AM -0600, /dev/rob0 wrote:
        > On Tue, Dec 04, 2012 at 11:59:01PM +1300, Peter wrote:
        > > I would still also set up port 587 on the mail.example.com
        > > IP as submission as well and try to encourage your users (at
        > > least the ones you can) to use port 587 from now on.
        >
        > What I would do, on Linux with IPv4 only, is create the submission
        > port and use an iptables redirect for the alternate IP address:
        >
        > # iptables -vt nat -A PREROUTING -p tcp --dport smtp -d \
        > mail.example.com -j REDIRECT --to-port submission
        >
        > This saves the overhead (system and administrative) of running
        > another smtpd on [mail.example.com]:25; he can leave his "smtp ...
        > smtpd" service alone in master.cf.

        Or better yet: replace it with postscreen.

        > I should also add as a reply to Stan in the other subthread: look
        > above at the first quoted paragraph: "Outlook Expresses setup with
        > ... default configuration."
        >
        > Yikes, bad news, very bad. If not doing content filtering nor
        > policy limitation of submission now, he will be soon. And possibly
        > losing his job in any case. Tomas is not in a good place right now.

        To clarify, I meant that if those Outlook Expresses are not yet
        compromised by malware, they will be, soon.
        --
        http://rob0.nodns4.us/ -- system administration and consulting
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