Re: et.al., (was: Dependencies et al, was: Default Debian install harassed me)
On Tue, 8 Oct 2019 00:25:44 -0500
David Wright <deblis@lionunicorn.co.uk> wrote:
> >
> > "subscribed.address" is the HELO and can be what I want it to be.
> > See the headers of my previous mail.
>
> Why would you use a "subscribed.address" (presumably an email address)
> for your HELO (presumably actually a EHLO). I was under the impression
> that it should be a domain, ie a FQDN.
It should actually be a hostname, it's the official public name of the
mail server, though not of course its local network name. It must be
resolvable in public DNS. In practice, not much of this is enforced,
and you can get away with a domain name and, apparently, an email
address.
It's a while since I did any email diagnostics, but certainly the HELO
pretty much only had to exist, it didn't seem to be checked very much.
I have seen email from a Small Business Server refused because the
default HELO was the invalid domain name xxxxx.local, as someone had
forgotten to set it properly. I can't be bothered (i.e. I haven't had to
do it yet) setting different HELOs for each domain that I use, and it
has never been a problem.
Neither does the MX record have to match any email address, nor the PTR
record for the sending IP address. There are many complex setups where
a business might send through one third-party SMTP server and receive
through the SMTP server of a mail-cleaning service, for example. The
only constraint (again, so far) on a sending address PTR is that it must
have a complementary A record, which does not have to be the address
that the MX points to or anything related to the email itself. Many ISPs
cannot handle multiple PTRs for the same IP address, at least not in
their user control panels, though they are permitted by RFC.
--
Joe
Reply to: