Re: [tlug] [slightly OT] SMTP and the internet, protocols and the internet

[Christian Horn <chorn@example.com>]

Hoi,

On Mon, Jan 11, 2021 at 02:35:33PM +0000, Schwartz, Fernando G. | @SCA wrote:
> 
> ... The machine " FQDN " must be " fluxcoil.net ". That's what the website
> test error refers to.
> BTW, for [f]ully [q]ualified [d]omain [n]ame of the host machine, I'd
> recommend:
> < some name for the machine > + < domain name >. Therefore, not just "
> fluxcoil.net " but rather, let's say, " mail.fluxcoil.net ".

You are right, one detail about the mail config was not in order,
but I fixed it and talked with t-online, that is not the issue.
They 'demand' full address and name on my webpage to accept mails
from me.

More verbose on what was misconfigured:
As of yesterday, I had this:
- MX record for fluxcoil.net was pointing at mail.fluxcoil.net
- mail.fluxcoil.net had an A record to my server
- the postfix was acting as 'fluxcoil.net'
- and the IP reverse lookup was pointing at fluxcoil.net

So while it had not presented issues so far, these were not
aligned.  Now:
- MX record was not changed, also not mail.fluxcoil.net A record
- postfix is now acting as 'mail.fluxcoil.net'
- the IP reverse lookup is now pointing at mail.fluxcoil.net

This is not convenient as all reverse lookups for the IP will
now bring up mail.fluxcoil.net, even if these were related 
to other services, i.e. https.

That issue was what caused the warning on
https://mxtoolbox.com/diagnostic.aspx .

So it's basically back to my original issue: a provider has
setup rules asking me to publish my data, only then he will
accept mails from me.

Chris