Registration e-mail is received as a SPAM

[thom4parisot]

Headers content

X-Spam-known-sender: no
Subject: {SPAM 05.5} Open Data for Resilience Index: registration for user oncletom
X-Spam: spam
X-Spam-score: 5.5
X-Spam-hits: HTML_FONT_LOW_CONTRAST 0.001, HTML_IMAGE_RATIO_04 0.61, HTML_MESSAGE 0.001,
	  KHOP_DYNAMIC 1.997, ME_NOAUTH 0.01, MIME_HTML_ONLY 1.105,
	  SPF_HELO_SOFTFAIL 0.896, SPF_SOFTFAIL 0.972, LANGUAGES en,
	  BAYES_USED none, SA_VERSION 3.4.0
X-Backscatter: NotFound1
X-Backscatter-Hosts: 
X-Spam-source: IP='195.201.219.176', Host='static.176.219.201.195.clients.your-server.de'

It's likely the host sending the e-mail SPF and DKIM DNS settings are not aligned properly. Thus e-mail servers think the e-mail is sent by rogue machines.

I still have to investigate a clearer path to resolution.

Via @pzwsk, taken from #147.