Postfix – connect from unknown[ip.address]

One server I poke around on, has a number of postfix instances

(see: postmulti).

Interestingly, one instance was logging things like :

Oct 26 22:02:05 mail postfix-blah/smtpd[59158]: connect from unknown[]
Oct 26 22:02:05 mail postfix-blah/smtpd[59158]: CA9292EE2C0: client=unknown[]

Which makes you think perhaps Postfix isn’t able to do DNS lookups – even though it’s configured to do so.

After a bit of investigation —

  1. DNS resolution on the host itself works fine.
  2. Postfix is running smtpd in a chroot (see /etc/postfix-blah/
  3. The ‘default’ Postfix instance (/etc/postfix, /var/spool/postfix) doesn’t have this problem.
  4. /var/spool/postfix-blah/lib doesn’t exist, but /var/spool/postfix/lib does and contains libnss_* files
  5. So, cp -a /var/spool/postfix/lib /var/spool/postfix-blah/lib fixes it.
  6. Turning off ‘chroot’ for the smtp daemon fixes it (edit: /etc/postfix-blah/

The  server is Ubuntu Lucid, so perhaps it’s a bit long in the tooth now – and maybe this problem won’t crop up for anyone else…



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One response to “Postfix – connect from unknown[ip.address]”

  1. fanosss Avatar

    Well some years later there’s a reply 😀

    Your smtp seems to work fine.
    The “unknown that you are getting means that the sender does not have a valid reverse DNS.

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