Re: domain names, was: hostname
On Tue 20 Mar 2018 at 17:07:47 -0500, David Wright wrote:
> On Fri 23 Feb 2018 at 16:18:29 (+0000), Brian wrote:
> >
> > With
> >
> > 127.0.1.1 gmail
> >
> > in /etc/hosts the conversation would go like this:
> >
> > brian@desktop:~$ telnet bendel.debian.org 25
> > Trying 82.195.75.100...
> > Connected to bendel.debian.org.
> > Escape character is '^]'.
> > 220 bendel.debian.org ESMTP Postfix
> > helo gmail
> > 250 bendel.debian.org
> > mail from:<someone@debian.org>
> > 250 2.1.0 Ok
> > rcpt to:<debian-user@lists.debian.org>
> > 504 5.5.2 <gmail>: Helo command rejected: need fully-qualified hostname
> >
> > gmail.com is ok with bendel.
> >
> > OTOH:
> >
> > brian@desktop:~$ telnet cloud11.unlimitedwebhosting.co.uk 25
> > Trying 149.255.60.164...
> > Connected to cloud11.unlimitedwebhosting.co.uk.
> > Escape character is '^]'.
> > 220 cloud11.unlimitedwebhosting.co.uk ESMTP Postfix
> > helo gmail
> > 250 cloud11.unlimitedwebhosting.co.uk
> > mail from:<someone@debian.org>
> > 250 2.1.0 Ok
> > rcpt to:<deblis@lionunicorn.co.uk>
> > 250 2.1.5 Ok
> > data
> > 354 End data with <CR><LF>.<CR><LF>
> >
> > cloud11.unlimitedwebhosting.co.uk appears not to be bothered by the
> > helo; bendel is.
>
> In common with a lot of home users, I can't connect to external
> machines on port 25. I assume that's because my ISP doesn't want
> to have their IP range affected by people spamming from it.
>
> Are the dialogues above meant to show that you're at liberty to
> insert emails into those hosts because you have/could have typed
> helo gmail.com at the prompt? Is that what an open relay is?
The two dialogues show that different mail servers treat what is
in the HELO/EHLO in two quite distinct ways. bendel cares what the
HELO/EHLO says; cloud11.unlimitedwebhosting couldn't care less. I
think both are RFC compliant.
The behaviour of cloud11.unlimitedwebhosting does not turn it into
an open relay.
--
Brian.
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