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:<some...@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:<some...@debian.org> > > 250 2.1.0 Ok > > rcpt to:<deb...@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.
