mail strangeness.

Jeremy Chadwick koitsu at
Mon Jan 28 17:56:39 PST 2008

On Mon, Jan 28, 2008 at 05:28:24PM -0800, Gary Kline wrote:
> Much closer to getting local mail [[ from]] working.   so far, 
> no mail, not even to test at gets thru.    If tis does, can anyone 
> explain the appended lines from /var/log/maillog....???   WHY is the "Helo 
> command rejected: Host not found"?  sendmail *is* rewriting my 
> <from=> linee to just "kline at THOUGHT.ORG" (sic) .   All caps intentionally.
> So far, I'm reaching friends, family,  and elsewhere.
> Jan 28 17:15:11 tao sm-mta[31683]: m0SMD6LO031117: 
> to=<freebsd-questions at FreeBSD.ORG>, ctladdr=<kline at> 
> (1002/1002), delay=03:02:05, xdelay=00:00:01, mailer=esmtp, pri=661432, 
> [], dsn=4.7.1, stat=Deferred: 450 4.7.1 
> <>: Helo command rejected: Host not found

This means that during the initial SMTP conversation, the following

* machine claiming to be connects to
* states HELO
* looks up the DNS A record of
* There is no such A record, so the SMTP server says sod off.

You either need to make actually have an A record (if
you're authoritative for that domain and have such abilities), or, you
need to pick a HELO hostname that actually resolves to something the
rest of the Internet can do lookups on.

Also, don't try to be sneaky and use something that resolves to a
reserved address (127/8, 192.168.0/16, etc.), because mailers will also
reject that assuming they use RHSBLs like or

Hope this helps, and welcome to present-day SMTP on the Internet, where
it's like pulling teeth (thanks, spammers!)

| Jeremy Chadwick                                    jdc at |
| Parodius Networking                  |
| UNIX Systems Administrator                      Mountain View, CA, USA |
| Making life hard for others since 1977.                  PGP: 4BD6C0CB |

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