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Re: Sending to a nolisting-enabled host

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  • Victor Duchovni
    ... This software is known to not work reliably with Postfix. ... sx.mail.vietnamfree.com has address 195.56.55.247 sx.mail.vietnamfree.com has address
    Message 1 of 7 , Oct 30, 2006
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      On Mon, Oct 30, 2006 at 01:49:10PM +0100, emailteszt wrote:

      > Oct 30 13:38:01 mail MailScanner[28292]: Requeue: 9B94C49365.737C7 to D2D3B4934A

      This software is known to not work reliably with Postfix.

      > Oct 30 13:38:01 mail postfix/qmgr[27761]: D2D3B4934A: from=<something@somehost>, size=1011, nrcpt=1 (queue active)
      > Oct 30 13:38:31 mail postfix/smtp[3206]: D2D3B4934A: host sx.mail.vietnamfree.com[195.56.55.34] refused to talk to me: 421 Server not available
      > Oct 30 13:39:01 mail postfix/smtp[3206]: D2D3B4934A: to=<valami@...&>, relay=sx.mail.vietnamfree.com[195.56.146.226], delay=66, status=deferred (host sx.mail.vietnamfree.com[195.56.146.226] refused to talk to me: 421 Server not available)
      >
      > The server's MX records:
      > host -t mx tvn.hu
      >
      > tvn.hu mail is handled by 6 mail20.vietnamfree.com.
      > tvn.hu mail is handled by 6 mail25.vietnamfree.com.
      > tvn.hu mail is handled by 6 mail30.vietnamfree.com.
      > tvn.hu mail is handled by 10 mail40.vietnamfree.com.
      > tvn.hu mail is handled by 5 sx.mail.vietnamfree.com.
      >
      > The sx.mail.vietnamfree.com is the non-working MX record. The second ones do work, but our smtp isn't using them.
      >

      sx.mail.vietnamfree.com has address 195.56.55.247
      sx.mail.vietnamfree.com has address 195.56.55.250
      sx.mail.vietnamfree.com has address 195.56.146.226
      sx.mail.vietnamfree.com has address 195.56.55.34

      The best-mx host has 4 IP addresses. Postfix will try these addresses before
      using any of the backup MX hosts.

      With Postfix 2.3, at most 5 addresses are tried by default, so after
      failing 4 times on the primary MX, there will be one more connection
      attempt with one of the preference 6 hosts. At most two delivery
      attempts are made with hosts that don't refuse to talk SMTP (220
      banner and 250 EHLO/HELO).

      smtp_mx_address_limit = 5
      smtp_mx_session_limit = 2

      With Postfix 2.1/2.2 (and perhaps 2.0), there is no limit on the
      number of addresses to connect to, but when the server issues a 220
      banner, and then a 4XX/5XX helo, this counts against the 2 session
      limit, rather than against the (default unlimited) connection
      limit. Servers with a 4XX/5XX banner are logged as "connect to
      <name>[<ip>]: server refused to talk to me: <banner>", while servers
      with a 4XX/5XX EHLO/HELO response are logged as "host <name>[<ip>]
      refused to talk to me: <HELO response>"

      smtp_mx_address_limit = 0
      smtp_mx_session_limit = 2

      Given your logs, we see that you are running Postfix 2.1 or 2.2 and the
      server is turning away connections during EHLO/HELO rather than with a
      4XX/5XX banner.

      The solution is to upgrade to Postfix 2.3 and perhaps set a somewhat
      higher:

      smtp_mx_address_limit = 10

      though in your case 5 is just enough to get past the non-cooperative host.

      --
      Viktor.

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      If my response solves your problem, the best way to thank me is to not
      send an "it worked, thanks" follow-up. If you must respond, please put
      "It worked, thanks" in the "Subject" so I can delete these quickly.
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