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Re: avoiding overload on port 587

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  • Ralf Hildebrandt
    ... That should be sufficient! -- [*] sys4 AG http://sys4.de, +49 (89) 30 90 46 64 Franziskanerstraße 15, 81669 München Sitz der Gesellschaft: München,
    Message 1 of 54 , Nov 30, 2012
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      * Robert Schetterer <rs@...>:
      > Am 30.11.2012 11:44, schrieb Tomas Macek:
      > > I cannot apply firewall rules on 587, because our clients travel with
      > > their notebooks and still want to send their emails through our mailserver.
      >
      > use fail2ban etc for blocking dynamic, brute force attacks to
      > submission, normally this never matched on legal clients cause they know
      > their passwords and submission should used only, with password auth and
      > tls , if afraid for dummy users, choose low blocking time

      That should be sufficient!

      --
      [*] sys4 AG

      http://sys4.de, +49 (89) 30 90 46 64
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    • /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
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        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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