Stephen Gran on 11 Oct 2005 08:22:24 -0000


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Re: [PLUG] exim4 and HELO host


On Mon, Oct 10, 2005 at 08:18:13PM -0400, Mark M. Hoffman said:
> I had a similar problem some months ago (except I use postfix).  I found
> out (by watching with ethereal) that Thunderbird just says:
> 
> 	EHLO [127.0.0.1]
> 
> So I modified /etc/postfix/main.cf to this:
> 
> 	smtp_helo_name = [10.17.17.3]
> 
> ...and all was working again.  Question to email gurus: is there anything
> wrong with that?

There are 2 'correct' (for some value of correct - the RFC's are fuzzy
about what is an acceptable HELO string) ways of doing this.  Either of
HELO fqdn or HELO [IP] - note that when you use your IP, you must use
the square brackets.

All that being said, many sites, like verizon and aol, are now refusing
mail based on the HELO string if it is unroutable or has other problems.
An address in RFC1918 address space would certainly qualify as 'having
problems', I would think.  If you want to send mail directly to other
sites, then you will want to make sure that forward and reverse DNS
match, and that you say HELO with whatever the fqdn of your rDNS is.
In other words:

216.158.52.10 = mail.lobefin.net
mail.lobefin.net = 216.158.52.10
my HELO string is mail.lobefin.net

I have several other addresses that resolve to 216.158.52.10, and
mail.lobefin.net actually resolves to two IPs at the moment, but the
rDNS only resolves to one fqdn, so that is the one to use.
-- 
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|  Stephen Gran                  | I think my career is ruined!            |
|  steve@lobefin.net             |                                         |
|  http://www.lobefin.net/~steve |                                         |
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