On Fri 23 Feb 2018 at 16:18:29 (+0000), Brian wrote: > On Thu 22 Feb 2018 at 11:58:18 -0600, David Wright wrote: > > > On Mon 19 Feb 2018 at 18:39:02 (+0000), Brian wrote: > > > On Mon 19 Feb 2018 at 10:23:56 -0600, David Wright wrote: > > > > > > > 127.0.0.1 localhost > > > > 127.0.1.1 alum > > > > > > alum is the canonical_hostname. It is used by exim to HELO with. Many > > > mail servers will not accept mail directly from you because it is not a > > > FQDN. > > > > This is why I wrote "broken" at ². The OP wrote "on a home LAN", > > in which case it's unlikely that they relay mail to mail servers > > on port 25. More likely is that they use a smarthost with a mail > > submission system on port 587 or possibly 465 (though 25 is > > allowed for broken senders³). > > Not using a smarthost does not invalidate the claim.
I got lost amongst the negatives and forgot all about this post until talk of spamming arose here. I don't understand why a home user would not be using a smarthost. Perhaps we're talking about a different group of people. Why would a home user want to relay mail rather than submit it to a smarthost? > > As submission involves obligatory authentication, there's no reason > > to reject a submission just because the HELO has no dot in it. And > > even if a sender screws up the envelope-from, it's likely that the > > mail submission knows a valid email address associated with the > > authenticator's registration details. > > 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? > > > > I've sometimes wondered what other people dream up as their > > > > domainnames; that is, people who don't have a legitimate reason > > > > to put something like example.com. > > > > > > Whatever is dreamt up as a domain name is put into /etc/hosts by the > > > installer as > > > > > > 127.0.1.1 alum.dreamtup alum > > > > And what is the benefit for the mail submission system in being woken > > up with HELO alum.dreamtup rather than HELO alum ? > > Extra brownie points for imagination perhaps. > > Most large ISPs presumably do not see any benefit as they basically > ignore an RFC non-compliant helo. The large number of broken mailers > about might be a reason. I'm not prepared to risk having mail rejected > because the canonical_hostname is not a FQDN known in the DNS. But are you a home user? (Not knowing anything about how you connect to the Internet, nor how you submit emails, I can't judge.) Cheers, David.
