Taking a quick look it doesn't appear the domain has an SPF record setup. This will help receiving mail servers block mail claiming to be from the domain but not sent from an explicitly authorized IP address. It's just a specially formatted zone record you can add if you have access. This tool (http://www.spfwizard.net) appears to make it pretty easy, though you'd probably figure it out after 10 minute on your own with the help of Google. I use http://www.mail-tester.com to verify I've got things configured right afterwards.

On Apr 29, 2017 4:34 PM, "Martin Owens" <doctormo@...400...> wrote:
On Sun, 2017-04-30 at 00:22 +0200, Maren Hachmann wrote:
> Oh :-( Does anyone know someone who could help?
>
> (I guess you've already checked that the server actually sent those,
> and that it wasn't just in the emails' 'From' field? - Sorry, that's
> the only thing I know about this..., there are people doing that with
> our private server, too. I think there is an option in the mail
> server settings that allows other email programs to request
> confirmation that the mail was actually sent from that server).

Hi Maren,

I suspect the emails weren't sent from our system, as the email
addresses that replied don't appear in our mail logs.

But I'm being cautious because the system isn't as secure as it could
be with an expert in the helm.

Martin Owens

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