On Fri, Jan 30, 2015 at 11:56:27AM -0500, James B. Byrne wrote:

> >> Jan 30 11:15:47 inet08 postfix-p25/smtpd[4796]: NOQUEUE: reject: RCPT
> >> from unknown[69.17.131.33]: 450 4.7.1 <mail4OA.4office.com>: Helo
> >> command rejected: Host not found; from=<x...@4office.com>
> >> to=<y...@harte-lyne.ca> proto=ESMTP helo=<mail4OA.4office.com>
> >>
> >> 33.131.17.69.in-addr.arpa. 19371 IN     PTR     mail4oa.4office.com.
> >>
> >> The dig was run on the host rejecting the mail.  Any ideas as to
> >> what is happening here?  Am I missing something obvious?
> >
> > The helo hostname, mail4OA.4office.com, does not exist.  You can
> > tell from the "helo command rejected: host not found" in the log.

Noel is absolutely right.

> And, as one can tell from the dig, mail4oa.4office.com. does exist. 

NO.  What the dig output shows is that a PTR record exists with
that name as the alleged holder of the address.

It completely fails to demonstrate the exitence of that host, which
DNS authoritatively says DOES NOT exist:

    $ dig +noall +comment +ans +auth +qu +nocl +nottl -t a mail4oa.4office.com
    ;; Got answer:
    ;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 59364
    ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

    ;; OPT PSEUDOSECTION:
    ; EDNS: version: 0, flags:; udp: 4096
    ;; QUESTION SECTION:
    ;mail4oa.4office.com.   IN A

    ;; AUTHORITY SECTION:
    4office.com.            SOA     toroon63nszp04.srvr.bell.ca. 
dns-admin.bellglobal.com. 8437 10800 3600 604800 1800

-- 
        Viktor.

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