On Sun, Jun 07, 2020 at 03:24:52PM +0000, lazuse wrote:
> On Sunday, June 7, 2020 3:11 PM, Ondřej Jirman <megatools@megous.com> wrote:
> 
> > On Sun, Jun 07, 2020 at 02:46:53PM +0000, lazuse wrote:
> >
> > > On Monday, June 1, 2020 6:55 PM, Ondřej Jirman megatools@megous.com wrote:
> > >
> > > > MX record is not necessary if the mail server is running on the same server
> > > > as pointed to by the A record.
> > >
> > > According to RFC 5321, 'the "implicit MX" rule above applies only
> > > if there are no MX records present. If MX records are present, but
> > > none of them are usable, this situation MUST be reported as an error.'
> > > In the case of megous.com, there exists an MX record vps.xff.cz.
> > > I am unsure how ProtonMail handled this situation, but my local
> > > OpenSMTPD reported it as an error and failed to deliver mails.
> >
> > It really looks fine to me, and the whole setup is almost
> > the simplest possible:
> >
> > -   my address is megatools@megous.com
> > -   megous.com MX is vps.xff.cz
> > -   vps.xff.cz A points to the address of the mail server
> >
> >     mxtoolbox score is pretty much perfect:
> >
> >     https://mxtoolbox.com/domain/megous.com/?source=findmonitors
> >
> >     Not sure what your OpenSMTPD complained about exactly.
> 
> I figured it was because I used Quad9 DNS on my server,
> which I am aware is not the best practice, but it is blocking
> your vps.xff.cz domain because of "ThreatConnect":
> 
> https://www.quad9.net/result/?url=vps.xff.cz
> 
> That is the reason I was under the impression that vps.xff.cz
> was a NXDOMAIN and that my mail failed to deliver.
> 
> Sorry about that.

Interesting. I've found no way to report false blocking on ThreatConnect's
website. What jokers.

regards,
	o.

> >     thank you and regards,
> >     o.
> >
> 
>