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Author: Simon Hobson
To: dng
Subject: Re: [DNG] ..devuan to the rescue? Easiest possible newbie email server setup, ideas?
Marjorie Roome via Dng <dng@???> wrote:

> I also end up rejecting a lot of spam because it lacks a reverse hostname (it's easily the largest category).
> So it's not just a few such as ntlworld and gmx that check this.

IIRC the specific complaint wasn't that they checked for rDNS, but that they matched it against the domain of the sender. That makes no sense at all, it prevents running more than one domain on one mail server.

I also use lack of rDNS as a check. I also check it for obvious misconfigurations like (from memory) : it's an IP literal (not allowed by RFC), it's not one of my domains, the domain actually exists.
But one thing I don't check is that the rDNS matches the name given by the server in it's greeting - that just gets too many rejections because to many supposedly professional IT people can't get basics right. And I don't just mean "little guys", some of the problems I've seen with DNS and mail servers have been from larger outfits where I know they employ sizeable IT departments.

Rick Moen <rick@???> wrote:

> :r! dig -t txt _dmarc.linuxmafia.com +short
> "DMARC: tragically misdesigned since 2012. Check our SPF RR, instead."

Thank you for brightening my day :-)

On 26 Sep 2020, at 04:53, Mark Rousell <mark.rousell@???> wrote:

> Ah, thanks. It does make deliverability easier to send via an established SMTP server such an one's ISP's server.

But then you :

a) lose all visibility of what happens to your mail
One of the reasons I use my own mail server is because I can then see exactly what's happening to my mail. Especially if it's not getting delivered - which these days doesn't generally seem to be a problem, even for AOL !
It also means I have evidence from my logs. On a number of occasions I've used this along the lines of "as per <blah, blah> which was delivered to your mailserver on <timestamp>" when dealing with people who have "conveniently lost" previous communications.

b) are reliant on your ISP being capable of running a mail server reliably.
I don't think I'm alone in finding ISP mail server offerings to "have shortcomings". I've personally lost mail due to incompetent ISPs.
As previously mentioned, unless you are expecting an email that doesn't arrive, you don't know you've lost it. I went through a phase where my ISP was losing mail, but only intermittently. It was only when I could pinpoint something missing, and the sender was tech savvy enough to be able to give me their server logs, did my ISP finally consider I had a complaint to investigate - they then went and changed my settings in their control panel to wrong settings, and lost mail that they'd had queued on the wrong server for some time (triggered delivery without any notice, but from the wrong server and my server rejected them as it only allowed mail specific servers (the ones they listed as inbound relays)).

But then, having run mail servers for some years now, I can really really understand the desire to make it an SEP (Someone Else's Problem) !