Re: [exim] bogus? helo godaddy --- <not!>

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Συντάκτης: Stanislaw Halik
Ημερομηνία:  
Προς: exim-users
Αντικείμενο: Re: [exim] bogus? helo godaddy --- <not!>
On Sat, Dec 02, 2006, Karl Schmidt wrote:
> Some of our mail would be sent from a MTA that did not have a MX
> record (This MTA would only respond to our public MTA and LAN
> computers). I suspect they did a reverse call-back based on IP address
> instead of MX record.


For hosts lacking an MX record, falling back to A/AAAA is the only
correct behaviour. Not that I condone blocking because of a failed
callout check.

>> 1. bogus helo


>> This means that the sending email server connected to our mail server
>> and said "HELO [their IP]". RFC 1132 says that the HELO ("hello")
>> message should contain "a valid principal host domain name for the
>> client host".


Holy RFC 2821 Quoteth:

-->--
4.1.3 Address Literals

Sometimes a host is not known to the domain name system and
communication (and, in particular, communication to report and repair
the error) is blocked. To bypass this barrier a special literal form
of the address is allowed as an alternative to a domain name. For
IPv4 addresses, this form uses four small decimal integers separated
by dots and enclosed by brackets such as [123.255.37.2] [...]
--<--

This should apply to HELO/EHLO just as well.

-- 
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