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Re: Helo command rejected: Malformed DNS server reply

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  • Wietse Venema
    ... The 0 indicates the MX host preference, and . indicates the MX host name. An empty string is not a valid hostname by my reading of RFCs, and therefore
    Message 1 of 3 , Aug 29, 2009
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      Jim Wright:
      > On Aug 28, 2009, at 5:50 PM, Noel Jones wrote:
      >
      > > Mail from yahoo.com is now rejected with:
      > >
      > > Aug 28 16:24:05 mgate2 postfix/smtpd[53002]: NOQUEUE: reject: RCPT
      > > from web34202.mail.mud.yahoo.com[66.163.178.117]: 554 5.7.1
      > > <web34202.mail.mud.yahoo.com>: Helo command rejected: Malformed DNS
      > > server reply; from=<yuser@...> to=<user@...> proto=SMTP
      > > helo=<web34202.mail.mud.yahoo.com>
      > >
      > > If we look up the helo name, we see:
      > > # host web34202.mail.mud.yahoo.com
      > > web34202.mail.mud.yahoo.com has address 66.163.178.117
      > > web34202.mail.mud.yahoo.com mail is handled by 0 .
      > >
      > > Apparently the bogus MX record triggers the reject. It also looks
      > > as if all of Yahoo!'s mail servers are configured with a similar MX
      > > record.
      >
      > My guess is that this record is malformed because 0 is not a valid IP
      > address. Sounds like Yahoo has some issues to work out.

      The "0" indicates the MX host preference, and "." indicates the MX
      host name. An empty string is not a valid hostname by my reading
      of RFCs, and therefore Postfix complains about it.

      I have backed out the changes that triggered the false rejects
      discussed in this thread, and have issued new Postfix releases.

      Wietse
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