Re: Decentralized reliable instant messaging?
On Tue, 30 Aug 2016 20:42:05 +0100
Brian <ad44@cityscape.co.uk> wrote:
> On Tue 30 Aug 2016 at 15:05:02 -0400, Henning Follmann wrote:
>
> > On Tue, Aug 30, 2016 at 05:49:34PM +0100, Joe wrote:
> > > On Tue, 30 Aug 2016 09:59:42 -0400
> > > Henning Follmann <hfollmann@itcfollmann.com> wrote:
> > >
> > > > On Tue, Aug 30, 2016 at 02:52:14PM +0100, Lisi Reisz wrote:
> > > > > On Tuesday 30 August 2016 14:05:36 Stefan Monnier wrote:
> > > > > > "shocked that anyone would want to design or use an
> > > > > > unreliable messaging system"
> > > > >
> > > > > Email is getting less and less reliable, so have you given up
> > > > > using it?? :-(
> > > > >
> > > > > Lisi
> > > > >
> > > >
> > > > However, why email is still reliable, because a proper setup
> > > > provides you with a well defined error messages (in case it is
> > > > not delivered).
> > >
> > > If an email is designated as spam, it will be *silently* dropped.
> > > It took mail admins a long time to realise that if a message was
> > > spam, the last thing they should do with it is to 'return' it to
> > > the apparent 'sender' as part of a bounce message.
> > >
> >
> > You have a much too simplistic view of todays anti-spam measures.
> >
> > If an smtp server tries to deliver a messages, usually the first the
> > receiving server does, during the helo, checking if the sending
> > server is blacklisted. If blacklisted any attempt to deliver any
> > mail will be denied and the sender will receive a proper 5XX error
> > message.
>
> brian@desktop:~$ telnet itcfollmann.com 25
> Trying 96.242.112.3...
> Connected to itcfollmann.com.
> Escape character is '^]'.
> 220 newton.itcfollmann.com ESMTP Postfix (Debian/GNU)
> helo spammershaven.com
> 250 newton.itcfollmann.com
> mail from:yourneighbourhoodspammer@gmail.com
> 250 2.1.0 Ok
> rcpt to:hfollmann@itcfollmann.com
> 450 4.2.0 <hfollmann@itcfollmann.com>: Recipient address rejected:
> Greylisted, see
> http://postgrey.schweikert.ch/help/itcfollmann.com.html
>
> I don't really want to go to the data command or go through this
> greylisting business but the helo command seems acceptable to your
> server.
>
It's a while since I did the telnet thing in anger, but I used to use a
well-known (in the UK) six-character helo to save typing. No server ever
pointed out to me that my mail-from had no connection with it. Many
servers will reject a non-existent helo hostname.
As you probably know, but others might not, it is recommended to reject
the mail at the Recipient stage even when the problem is something else
entirely. It's not likely to have been the helo here, as the result of
failure would probably not have been a greylisting. Some systems are
configured to greylist any previously-unknown sender, no matter how
squeaky-clean they are otherwise.
I don't know if that is true here, as I might gently point out the the
URL given does not work.
--
Joe
Reply to: