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Re: et.al., (was: Dependencies et al, was: Default Debian install harassed me)

On Tue, Oct 08, 2019 at 09:13:31AM +0100, Joe wrote:
> On Tue, 8 Oct 2019 00:25:44 -0500
> David Wright <deblis@lionunicorn.co.uk> wrote:
> > 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.

"Enforcement" is entirely up to the receiver's discretion.  Some receivers
use it as an anti-spam measure -- if your HELO string doesn't resolve,
they won't accept your connection.  I've even heard of receivers who
attempt to make an STMP connection back to the MX of your HELO domain,
to make sure you have a running incoming SMTP service.

Other receivers may simply log it, or ignore it altogether.

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