Re: Email Question - OT

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Allegedly, on or about 20 February 2019, William Oliver sent:
> The gist I got was that my domain resolved correctly, and the ICANN
> ownership info of the domain was correct, but the ownership of the
> some other component, like the IP address, was different, since it
> was tied to my ISP and not to me -- even though I was doing my own
> nameservice.

If the numerical IP address of your service is shared between
yourselves and others, whether that's because your IP can change at
different logins, or other's use it simultaneously (such as webserver
hosts that service many clients on the same numerical IP), you're not
going to get the host to point their reverse DNS look-up to your domain
name.  You need a permanently unique IP to be able to do that.  The
same situation applies for HTTPS and certificates (you need to be the
sole user of your IP).

For shared IPs, the reverse lookup is going to be set to a hostname
that suits the actual owner of the IP.

Related to the original problem, is a couple of the techniques used for
spam rejection:

If your recipients checks that the IP your mail came through is one
authorised to handle your mail, and that's not set, it'll be another
problem for you.  The domain name owner sets DNS SPF records listing
the authorised services its mail goes through.  This is something
within your control, if you have proper control of your DNS records.

And another anti-spam technique that's related to your IP is the range
of IPs known to be used by clients of ISPs is considered to be unsafe
to accept mail from (as opposed to the range of IP addresses that the
ISP's own mail services work from).  If your recipient, or the services
between you and the end-recipient, checks to see if you're using an
ordinary customer IP, then your mail can be rejected for those reasons,
too.

In short: 

1. You need a mail server on an IP that the rest of the world is
willing to receive mail from.  This will cost you more, and the average
consumer ISP might not be able to supply one to you.

2. Your forward and reverse DNS records should all return the same
information (the answer to, "What IP is your mail server at?" should be
the same answer as, "What is the hostname for the IP my mail server is
at?"  And your domain's MX record should point to your mailserver.

3. Your domain's DNS SPF records should list your authorised mail
services.  DKIM is a similar thing.

-- 
[tim@localhost ~]$ uname -rsvp
Linux 4.16.11-100.fc26.x86_64 #1 SMP Tue May 22 20:02:12 UTC 2018 x86_64

Boilerplate:  All mail to my mailbox is automatically deleted.
There is no point trying to privately email me, I only get to see
the messages posted to the mailing list.

Lucky for you I typed this, you'd never be able to read my handwriting.
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