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Google now blocks spoofed emails for better phishing protection
(www.bleepingcomputer.com)
This is a most excellent place for technology news and articles.
I know a there are a lot of issues with self-hosting email, but I just don't thing this is one of them. First, it probably won't affect a self-hosted servers anyway unless you send a lot of emails, this requirement is only for servers sending 5,000 messages daily to Gmail. And even if you are, the requirements are not that harsh, it's a couple DNS records and a DKIM signing daemon, and if you are using a pre-build email package like mailcow it's probably already doing it.