Deliverability
Authentication, reputation and the reasons mail does not arrive.
DMARC policy: none vs quarantine vs reject
What p=none, p=quarantine and p=reject each ask a receiver to do, how pct, sp and rua shape the policy, how to read reports, and the safe order to move up.
Custom return path: why your bounces need it
What the return path is, how it differs from the From header, why putting it on your own subdomain makes SPF align under DMARC, and the two records that do it.
Email suppression list: what it is, how to use it
What an email suppression list holds, how bounces and complaints add to it, why a suppressed send still answers 200, and how to import a list from elsewhere.
DKIM, SPF and DMARC explained for developers
What SPF, DKIM and DMARC each prove, the records to publish, how alignment ties them together, and what the large mailbox providers now require of senders.
Hard bounce vs soft bounce: what to do with each
A hard bounce is permanent, a soft bounce is temporary. What causes each, what the reply code tells you, when to retry, and when to suppress an address.
Email deliverability guide for developers
Delivered is not the same as inboxed. Authentication, domain reputation, list hygiene, the headers bulk senders need, and the numbers worth watching every week.
Email domain verification, step by step
What verifying a sending domain proves, which DNS records to publish, the name-suffix trap that catches everyone, and what to do when a record will not verify.
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