Re: [exim4] Testing and making sense of smtp output
On Mon, 13 Oct 2014 10:25:37 +0100
Brian <ad44@cityscape.co.uk> wrote:
> On Mon 13 Oct 2014 at 04:06:27 +0200, lee wrote:
>
> > Harry Putnam <reader@newsguy.com> writes:
> >
> > > lee <lee@yagibdah.de> writes:
> > >
> > > [...]
> > >
> > > Thanks for the tips.
> > >
> > >>> SMTP>> EHLO 2xd
> > >
> > >> That's an invalid helo string.
> > >
> > > Is a valid one made up of just the full fqdn?
> >
> > See https://tools.ietf.org/html/rfc2821#section-4.1.1.1
> >
> > It says to either use the fqdn or, if not possible, an IP
> > literal. However, it's common practise to deny IP addresses in HELO
> > greatings.
>
> An address literal is not the same as an IP address. An MTA should not
> be rejecting mail on the basis that the HELO is an address literal.
>
> It's probably academic what the HELO is most of the time. Many ISPs
> will accept any old rubbish for it.
>
>
The routine exim4 HELO test is disabled by default, but simply checks
that it is a hostname which can be resolved in public DNS. I enable it,
and so do a lot of others. It is by default enabled in Exchange, which
is in widespread use, and I've seen an Exchange server reject an email
arriving from a BT server which had a '.local' TLD in its HELO.
--
Joe
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