[Cialug] MTA HELO

[Kevin Smith]

Just so it's clear. A lookup of any kind doesn't happen. It's just checks
syntax.

Relevant Postix settings:
reject_non_fqdn_helo_hostname (with Postfix < 2.3: reject_non_fqdn_hostname)
Reject the request when the HELO or EHLO hostname is not in fully-qualified
domain or address literal form, as required by the RFC.
mail.whatever.foo would actually pass.
"whatever" would fail.
[123.123.123.12] would pass as well I think, until it reached below...

reject_invalid_helo_hostname (with Postfix < 2.3: reject_invalid_hostname)
Reject the request when the HELO or EHLO hostname is malformed.
[123.123.123.12] would fail.
"mail/whatever.foo" would fail.
etc...

The following would do a DNS lookup, but it wouldn't be compliant with RFC
to reject based on that, so it's rarely used and neither do I.

reject_unknown_helo_hostname (with Postfix < 2.3: reject_unknown_hostname)
Reject the request when the HELO or EHLO hostname has no DNS A or MX
record.


On Sun, Jan 12, 2014 at 1:28 PM, Paul Gray <gray at cs.uni.edu> wrote:

> On 01/12/2014 01:25 PM, Kevin Smith wrote:
> > Again it's not a DNS issue.
>
> Completely disagree.  If the host in the HELO was resolvable, you'd have
> no problem.
>
> -PG
>
>
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