Ich habe seit kurzem das Problem, dass viele Emails, die von unserer Seite (https://fotoqkd.piwigo.com/admin.php?pa … =subscribe) mit folgender Information abgelehnt werden:

This is the mail system at host piwigo.com.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

The mail system

Beispiele:
<xxx@t-online.de>: host mx01.t-online.de[194.25.134.72] said: 559 5.1.9
    (DKIM reject DKIMr) Missing, invalid or non-matching DKIM signature (in
    reply to end of DATA command)

<xxx@gmail.com>: host gmail-smtp-in.l.google.com[74.125.133.27] said:
    550-5.7.26 This mail has been blocked because the sender is
    unauthenticated. 550-5.7.26 Gmail requires all senders to authenticate with
    either SPF or DKIM. 550-5.7.26  550-5.7.26  Authentication results:
    550-5.7.26  DKIM = did not pass 550-5.7.26  SPF [qwankidoberlin.de] with
    ip: [87.98.133.140] = did not pass 550-5.7.26  550-5.7.26  For instructions
    on setting up authentication, go to 550 5.7.26
    https://support.google.com/mail/answer/ … entication
    l21-20020a7bc455000000b004076263487fsi8864090wmi.77 - gsmtp (in reply to
    end of DATA command)

<xxx@gmx.de>: host mx01.emig.gmx.net[212.227.17.5] refused to talk to
    me: 554-gmx.net (mxgmx117) Nemesis ESMTP Service not available 554-No SMTP
    service 554-Bad DNS PTR resource record. 554 For explanation visit
    https://www.gmx.net/mail/senderguidelin … amp;c=rdns

Bis zum Sommer geschah die nur bei GMX, jetzt auch bei Gmail und t-online. Was muss ich einstellen, damit die Nutzer wie bisher  eine Benachrichtigung erhalten?