Getting mail into the inbox: authentication, reputation, spam scoring, and what the big providers actually check.
3 articles
Google and Yahoo's sender requirements, translated from policy into engineering: SPF and DKIM on the right domains, DMARC, aligned From headers, one-click unsubscribe, TLS, reverse DNS and the spam-rate ceiling — and how to verify each one on a message before it goes out.
What List-Unsubscribe and List-Unsubscribe-Post do, why Gmail and Yahoo now require them, what your endpoint must accept, which messages should carry them and which must not — with working code for Laravel, Node.js and Python.
What a SpamAssassin score of 4.2 actually means, where the 5.0 threshold comes from, the rules that fire most often on transactional email, how to read the X-Spam-Status header, and what to fix in the template versus the infrastructure.
See it on your own mail
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