As mentioned on otrs-en-l, ticket 2018010410009047 was complaining about emails purportedly from email@example.com with blatant advertisements.
Currently, wikipedia.com records are:
SPF: "v=spf1 include:wikimedia.org ~all"
DMARC: "v=DMARC1\; p=none\; sp=none\; rua=mailto:firstname.lastname@example.org\; ruf=mailto:email@example.com\;"
Given that I don't think we have used any @wikipedia.com email address for at least the last 10 years, I propose strengthening them to spf -all and dmarc p=reject, so at least we send a clear signal to the email providers that those emails are not related to us.